VIA UNIVERSITY COLLEGE, HORSENS, DENMARK
Noise Control
Construction Principles for Acoustic Attenuation
7th Semester Final Dissertation
Author: Ivan Donchev
Consultant: Søren Frederiksen
Bachelor of Architectural Technology and Construction Management
October 2014
TITLE PAGE
Report Title: Noise Control. Construction Principles
for Acoustic Attenuation
Supervisor: Søren Frederiksen
Author: Ivan Asenov Donchev
Date/Signature: 24 October 2014
Student Number: 163632
Issue: Final
Page Count (2400 characters/page): 30
GENEREL INFORMATION: All rights reserved - ingen del af denne
publikation må gengives uden forudgående tilladelse fra forfatteren.
BEMÆRK: Denne rapport er udarbejdet som en del af uddannelsen til
bygningskonstruktør – alt ansvar vedrørende rådgivning, instruktion eller
konklusion fraskrives!
Ivan Donchev
24 October 2014
1. Preface
This report was written as a mandatory final dissertation project in the 7th
semester of the professional bachelor degree Architectural Technology and Construction
Management at VIA University College, Horsens, Denmark. It was completed while
working full time for the architectural company NS Architects LTD based in Liverpool,
England. The report deals with the current construction principles and solutions to
acoustics and sound attenuation in both new built and refurbishment works. The
research was done with the help of internet sites, books, other written reports dealing
with problems similar to the one in hand, and with the special help of my personal
consultant Søren Frederiksen, my work colleague and good friend Richard Jones, my
current managing director Nick Serridge, and my girlfriend Aimée Mills.
1.1 Disclaimer
It is prohibited to directly use any of my work done in this report without my
consent. I do not assume any responsibility for any type of detriments or unfavorable
outcomes that may or may not occur in case of someone following my recommendations
or construction principles explained in this report. Everything stated within these pages is
written with self-study purposes and I do not claim that it is 100% accurate or viable, nor
do I firmly stand behind the validity and credibility of the sources of information used.
2. Abstract
Sound is inevitably generated within the confines of any building. Whether it is
people, the construction’s service pipes and generators, or machinery, noise will be an
annoying factor to most individuals. Not only can it lead to an unhealthy living or working
environment, sound can adversely affect the occupants of the building. Acoustics is an
aspect of the building design that inevitably needs to be addressed at some point in the
planning stages of any project. This report attempts to seek out different construction
principles that can be used to minimize the spread of sound to areas within the building
where it is not desired. Most of those solutions can be applied to any sort of project –
newly proposed construction, renovation works, change of purpose of an existing
building, etc. The report also tries to find out the physics behind sound travel, briefly
explains the negative effects of prolonged exposure to noise on humans, and clarifies
certain terminologies relevant to sound. The aforementioned is researched and included
in this report in order to fully comprehend the need for constructing architects to
incorporate an acoustic strategy to any of their future projects. Those results were found
with the help of many reliable sources, all of which contribute to the final discoveries.
3. Key Words
Acoustics, sound, attenuation, reverberation, decibel, frequency, absorption, spread.
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Table of Contents
1.
Preface........................................................................................................................................ 3
1.1
Disclaimer ........................................................................................................................... 3
2.
Abstract ...................................................................................................................................... 3
3.
Key Words .................................................................................................................................. 3
4.
List of Illustrations ...................................................................................................................... 5
5.
Introduction and Problem Formulation ..................................................................................... 6
6.
7.
8.
5.1
Introduction ....................................................................................................................... 6
5.2
Reasoning Behind Topic Choice ......................................................................................... 6
5.3
Main Research Topic .......................................................................................................... 6
5.4
Secondary Research Topics ................................................................................................ 6
5.5
Delimitation ........................................................................................................................ 7
5.6
Theoretical Basis and Sources ............................................................................................ 7
5.7
Research Methodology and Empirical Data ....................................................................... 7
The Essence of Sound ................................................................................................................. 8
6.1
What is Sound? (part 1)...................................................................................................... 8
6.2
Terminology ....................................................................................................................... 9
6.3
What is Sound? (part 2).................................................................................................... 11
6.4
Sources of Sound .............................................................................................................. 12
6.5
Room Modes .................................................................................................................... 13
6.6
Reverberation Time .......................................................................................................... 15
6.7
STC Scale........................................................................................................................... 17
Negative Effects of Noise ......................................................................................................... 18
7.1
Hearing Defects ................................................................................................................ 18
7.2
Sleeping Disorders ............................................................................................................ 19
7.3
Cardiovascular Issues ....................................................................................................... 19
7.4
Mental Illness ................................................................................................................... 20
7.5
Impairment of Cognitive Development............................................................................ 20
7.6
Annoyance........................................................................................................................ 20
Construction Principles for Sound Attenuation ....................................................................... 21
8.1
Sound Travel through the Building................................................................................... 21
8.2
Basic Construction Treatment Methods .......................................................................... 22
8.3
Building Regulations Demands ......................................................................................... 23
8.4
Floor Construction Details and Systems........................................................................... 24
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Wall Construction Details and Systems............................................................................ 29
Conclusion ................................................................................................................................ 33
Bibliography ..................................................................................................................................... 34
Table of Contents – Appendices....................................................................................................... 39
4. List of Illustrations
Fig.1 (p.9) <http://www.aplusphysics.com/courses/regents/waves/images/Wave-Anatomy.png>
Anatomy of a wave
Fig.2 (p.10) <http://www.solitaryroad.com/c1030/ole3.gif > Longitudinal and transverse wave
Fig.3 (p.11) <http://www.physicsclassroom.com/Class/sound/u11l1c1.gif> Compressions and
rarefactions
Fig.4 (p.13) <http://i227.photobucket.com/albums/dd269/glennkuras/RoomModeGraphic.jpg >
The three types of room modes
Fig.5 (p.13) <http://artsites.ucsc.edu/ems/Music/tech_background/TE02/modes/Modes_files/image018.png > Room modes formula
Fig.6 (p.13) <http://artsites.ucsc.edu/ems/Music/tech_background/TE-02/modes/Modes.html >
p, q, r values table
Fig.7 (p.14) <http://artsites.ucsc.edu/ems/Music/tech_background/TE-02/modes/Modes.html >
Example room mode calculation
Fig.8 (p.17) <http://www.soundproofingcompany.com/wpcontent/uploads/2011/06/understading_stc_chart_data.gif> STC graph with plotted curves
Fig.9 (p.18)
<https://lh6.ggpht.com/BSRe58tB72KMMuesbUswRz7x6SQwJskdns2vslsHpOOe9LvRpMuzTViRO7zfhIfKN1_AA=s170> STC graph comparing two wall constructions
Fig.10 (p.21) <http://www.greengluecompany.com/sites/default/files/banner_img06.jpg > Sound
travel through construction
Fig.11 (p.22) <http://www.bre.co.uk/pdf/soundins_homes.pdf > Remedial wall treatment
Fig.12 (p.22) <http://www.bre.co.uk/pdf/soundins_homes.pdf > Remedial ceiling treatment
Fig.13 (p.25) <http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADE_2003.pdf > Resilient
layer treatment method
Fig.14 (p.26) <http://www.instacoustic.co.uk/media/3496/c40-drawing-a.jpg> Cradle system
treatment method
Fig.15 (p.27) <http://www.forboflooringna.com/Commercial-Flooring/Products/Flotex/ > Textile
carpet treatment method
Fig.16 (p.28) <http://www.instacoustic.co.uk/media/7247/Combination-TimberFloor.jpg >
Combination system
Fig.17 (p.28) <http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADE_2003.pdf > Cavity
stop
Fig.18 (p.30) <http://www.british-gypsum.com/~/media/Files/British-Gypsum/WHITEBOOK/WHITE-BOOK-Full-Publication.pdf > 69dB stud wall
Fig.19 (p.32) <http://www.acousticalsurfaces.com/acoustic_windows/acoustical_windows.htm>
High-performance acoustic windows (Villanueva, 2010)
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5. Introduction and Problem Formulation
5.1 Introduction
Just like light, sound is one of the fundamental elements in the environment of
existence. Thunder and lightning go hand in hand. Present everywhere in nature, sound
plays a vital role in the evolution of most living creatures. It serves as a medium for
information exchange, manifestation of feelings, sharing of ideas, and expression of
beliefs and self. Although loud and startling noises are part of natural surroundings, only
in recent centuries has much of the world become increasingly urban and chronically
noisy. The three main pollution types – air, light, and sound are part of any given
metropolitan environment and all of them are of a direct result of human evolution and
the betterment of human life. Sound plays a fundamental part in the everyday lives of
humans. Not only do we use it to communicate with each other, it has become a way of
amusement as well – watching movies, dancing, telling jokes, singing, even the simple act
of taking a shower, and of course one of the greatest pleasures we derive from sound –
music, generate certain decibel levels. Sound is good, sound means you are alive, sound
means you are having fun and you are part of society. It all seems very promising;
however, the abundance of it and the presence of it where not wanted can become quite
annoying and unhealthy at times. In our current living environment and lifestyle, intrusive
sound is gradually causing more discomfort to the average citizen. This brings out the
need for containing noise within a desirable area and thus ensuring the comfort and
privacy of people in close proximity to the source. This need is addressed by the people
accountable for the planning of any building – the constructing architects.
5.2 Reasoning Behind Topic Choice
As a future constructing architect, one of my many responsibilities will be to
ensure sound is being properly compartmented and the spread of it throughout the
building is minimal if not inexistent. It is our responsibility to face those complications and
take the action we deem necessary and most reasonable. As a person who has already
researched the topic of light pollution in the past, I find it only fitting to investigate the
problem of sound pollution as well. I believe this to be an important aspect of the design
process and the finds in this report can be directly applied to several projects I am
currently involved in. One of those projects requires quite an extensive research on
acoustics as this is one of the main problems our company is faced with; therefore, this
report will be beneficial to the job in hand.
5.3 Main Research Topic
 What are the different construction principles and acoustic strategies that
constructing architects can adopt in order to minimize sound travelling
through the building?
5.4 Secondary Research Topics
 What is sound?
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

What are the characteristics of sound?
How does unwanted sound adversely affect people?
5.5 Delimitation
As already stated, most of the solutions, if not every single one, can be applied
anywhere. No matter if the need is for a new build project or a renovation one, the
construction principles are fundamentally similar. This report, however, does not deal
with specific acoustic strategies for projects where there is a need for sound to actually
be boosted, rather than minimized. Places like opera houses and concert halls, where the
term acoustics is used in a sense of achieving a “good” sound within a building will not be
discussed. Even though the main aim of this report is to learn of ways to control sound,
this feature of it is not intended.
5.6 Theoretical Basis and Sources
The research will be carried out using both primary and secondary sources.
Tertiary sources will not be used. The resources used will be focused on published books,
trusted sites, as well as guidance notes or papers written on the subject of acoustics and
sound attenuation. Where applicable, both Danish Building Regulations, and United
Kingdom Building Regulations will be observed and documented, since the projects I plan
on applying my finds to, are based within the United Kingdom. All observations, finds, and
conclusions will be seen through both design and environmental point of view.
5.7 Research Methodology and Empirical Data
The data presented will be of equal parts qualitative and quantitative. Since sound is
something that needs to be measured in order to judge the reliability of different
construction principles stating that they reduce sound levels, numbers will play a big part
in this report. On the other hand, people’s opinions and observations, as well as the
quality of different building materials used matter too. A fair balance between the two
will be sought out.
“I spend several days at a time without enough sleep. At first, normal activities
become annoying. When you are too tired to eat, you really need some sleep. A few days
later, things become strange. Loud noises become louder and more startling, familiar
sounds become unfamiliar, and life reinvents itself as a surrealist dream.”
Henry Rollins, American musician and writer
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6. The Essence of Sound
In order for any of the researched construction details and strategies to be fully
and undoubtedly comprehended, it is of the utmost importance to have a broader
understanding of sound and its qualities.
6.1 What is Sound? (part 1)
Sound is one of the many elements in physics. And as most of the elements in
physics, it is closely related to the realm of energy. Just like light being emitted from a
source, or the transmission of a radio broadcast, sound is simply energy being propagated
by waves. This energy requires a source, the cause being a disturbance within the
medium of propagation of the wave. (Loten, W.). A stone dropped in water creates a
ripple effect. The result is several identical waves travelling at equal distances away from
the source, propagating the energy created by the stone disturbing the natural
equilibrium of the water’s surface. Even though it looks like the water is in effect moving,
it is actually the energy of the disturbance that moves. (Loten, W.). Just like with water
waves, sound is created in a similar fashion. A thud by a fist on a desk produces a certain
amount of energy that begins its journey outward of the source (in this case, the point of
impact between the fist and the desk). The energy is pushing the air molecules back and
forth in parallel to the wave motion manner. (Loten, W.). Travelling at equal rates and in
all directions, the waves eventually reach a receiver – a human ear for example. The
second the waves reach the ear, the organ itself begins vibrating in the exact same way as
the origin waves. By doing so, it sends electrical impulses to the brain, which in turn
interprets the waves as sound. The duration and intensity, or loudness, of the sound
depends greatly on the initial conditions, the medium, and the amount of source energy.
(Smith, T.). Waves will no longer be propagated once equilibrium is reached again. All
returns to a state of rest and the energy dissipates. For this whole process to work as
explained, a vital component must always be present – a medium in which the waves can
travel. Without a medium like air, or water, or a solid (steel, wood, concrete, etc.) there
are no molecules to bump into each other and transmit the energy created by the
disturbance. A bell hermetically sealed in a vacuum chamber can be struck many a times;
however, no sound will be generated since there are no air molecules to propagate the
waves. (Smith, T.). Sound most frequently travels in the medium of air. When people
communicate with each other, they vocally express their thoughts and ideas. Even though
it is harder to imagine sound waves in air, due to the fact that they cannot be seen, a
simple experiment proves that they exist. By striking a tuning fork and changing its
medium by dipping it slightly in water, the ripple effect is created and not only can a
sound be heard, it can also be seen on the surface of the water. In this case, the energy is
propagated in two different mediums – it travels in air, thus we can hear it, and in water –
we can observe it. (Loten, W.). The simplest definition that one can give about sound is
that of a wave travelling through a medium caused by the release of energy after a
disturbance of the natural state of the source. The following section deals with some of
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the characteristics and properties of sound, as well as important for this report
terminology.
6.2 Terminology
The following are listed alphabetically.

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amplitude (fig.1) – the
maximum displacement of
a point on a vibrating object
measured
from
its
equilibrium position. For a
transverse
wave
the
fig. 1 Anatomy of a wave
amplitude is measured by
the displacement of any point on the object from its position at rest. For a
longitudinal wave the amplitude is measured by the displacement of a particle
from its position at equilibrium. (Britanica).
decibel [dB] – the unit used to measure the intensity level of sound.
(Physicsclassroom).
compressions – areas of high molecule pressure within a longitudinal wave.
(Physicsclassroom).
crest (fig.1) – the highest part of a wave within a cycle. (Thefreedictionary).
echo – the delayed arrival of a reflected sound which arrives to the listener’s ear
with a slight time delay. As sound travels within a room, the waves strike different
surfaces (walls for example). Some of the energy of the wave is absorbed by the
wall. Some is transmitted through its surface. The rest bounces back and reaches
the ear again. (Aes).
equilibrium (fig.1) – the undisturbed state of a medium. The equlibrium level on
figure 1 is shown as a straigh line. (Britanica).
frequency – the amount of particle vibrations over a fixed period of time within a
medium, or in other words, how often an event occurs. For example, a hand
moving back and forth over the surface of still water two times within a second
creates two waves (or cycles) every second. This rate of 2 cycles/second is the
frequency. Frequency is measured in Hertz [Hz] where 1 Hz is equivalent to 1
cycle/second. In the previous example, if the hand was creating 9 waves within 3
seconds, the frequency would be 9 divided by 3, equaling 3 cycles/second or 3 Hz.
(Physicsclassroom). Humans brains can process waves and interpret them as
sound in the range of 20 to 20 000 Hz. In other words, humans can perceive from
20 waves a second to 20 000 waves a second. Dogs can hear up to 40 000 Hz,
while bats up to 100 000 Hz. (Loten, W).
herz [Hz] – the unit used to measure frequency. (Physicsclassroom).
intensity – the amount of energy that is transported past a given area of the
medium over a certain period of time. Since sound waves are introduced into a
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medium by the vibration of an object, their intensity is dependent on the intensity
of the vibration. The more energy introduced in the initial disturbance of
equilibrium, the higher the vibration, therefore the higher the amplitude of the
wave. The formula used for calculating intensity is energy/time x area. The typical
unit used to express intensity is Watts/m². Human ears can detect an intensity as
low as 1*10-12 W/m². A sound with such intensity corresponds to the displacement
of an air particle by as little as one-billionth of a centimeter! This is the lowest
intensity sound a human ear can detect and it is known as the threshold of hearing
(TOH). Since humans can detect intensities that are extremely vast, a scale based
on powers of 10 is used to measure intensity. This scale is known as the decibel
scale. The TOH has an intensity level of 0dB. A sound that is 10 times as intense
(1*10-11 W/m²) has an intensity level of 10dB. A sound 100 times more intense
than TOH (1*10-10 W/m²) has a level of 20dB and so on. A whisper has an intensity
level of 20dB, while a normal conversation is at 60dB, and the front rows of a rock
concert peak at 110dB. The threshold of pain for human ears is 130dB.
(Physicsclassroom).
longitudinal wave (fig.2) – a wave in which the
particles of the medium vibrate in a parallel
fashion to the direction of the wave motion. The
energy is transported by the constant change of
compression and expansion within the particles
in the medium. (Miller, J.).
fig. 2 Longitudinal and transverse wave
rarefactions – areas of low molecule pressure
within a longitudinal wave. (Physicsclassroom).
resonanse frequency – a frequency under which an object vibrates heavily. (HSW).
reverberation – a series of multiple echoes that gradually decrease in intensity.
The multiple echoes become more and more closely spaced with time that they
become one continuous sound which is eventally absorbed by the inner surfaces
of a room. The difference between and echo and reverberation is that an echo is a
discrete repetition of a sound, while reverberation is the continuous fade-out of
that sound. (Aes).
reverberation time – the time it takes for sound to decay to 60dB below the
original sound level. It is abbreviated as RT60. (Aes).
room mode – the response of a room to different frequencies caused by sound
bouncing off the walls. Rooms can both boost and dampen certain sound
frequencies depending on the room’s shape and size. For more information, refer
to section 6.5 Room Modes in this report on page 13. (Gikacoustics).
transverse wave (fig.2) – a wave in which the particles of the medium vibrate in a
perpendicular fashion (at right angles) to the direction of the wave motion.
(Miller, J.).
trough (fig.1) – the lowest part of a wave within a cycle. (Thefreedictionary).
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velocity – the speed with which sound travels through a medium. The velocity is
highly dependent on the properties of the medium. Since sound is the energy
being propagated by particles colliding with each other, the closer the particles
are packed next to each other, the faster the propagation. Therefore, the speed of
sound in solids is greater than the one in liquids, which in turn is greater than the
one is gases. For example, steel conducts sound much faster than air. Sound
velocity also depends on the elastic properties of the material which it travels
through. Those elastic properties determine how easy it is for said material to
maintain its shape. Steel will exert very little deformation when pressure is applied
to it; it has high elasticity, while rubber will easily deform under stress; it has low
elasticity. The higher the elasticity, the faster the velocity of sound. Initial
conditions also affect the speed of sound. For example, as the temperature and
humidity of air varies, so does the compactness of air molecules. This changes the
particle interaction and elasticity. The speed of sound in dry air and normal
atmospheric pressure is calculated using the formula v = 331 m/s + (0.6 m/s/C)xT,
where T is the current temperature in Celsius. Typically, 20 ° C is used as standard
initial condition. Therefore, the speed of sound through air is 331m/s + 0.6m/s x
20 equals 343m/s. (Physicsclassroom).
wavelength (fig.1) – the distance between two adjacent, identical and easily
identifiable points within a wave cycle. Such easily identifiable points can be the
wave crests or troughs. Wavelength can be calculated using the formula λ = v / ƒ,
where v represents the velocity and f represents the frequency. For example, the
wavelength of a 440Hz sound wave travelling through air is 343 meters per second
divided by 440Hz equals 0.7795 meters or nearly 78 centimeters between crests.
(Techterms).
6.3 What is Sound? (Part 2)
Now that some of sound’s main characteristics and terminologies have been made
clear, a more sophisticated rather than a simplistic definition can be given. Sound is a
mechanical pressure wave that is the result of the back and forth vibration of particles
through a medium. (Villanueva, J.). The wave type of sound is a longitudinal one.
Therefore if a sound wave is moving from left to right, the particles will be displaced in
both leftward and rightward directions (parallel and anti-parallel to the wave motion,
rather than perpendicular). Due to this
longitudinal motion, there are regions
within the air where the molecules are
compressed together, or further apart.
Those regions are known as compressions
and rarefactions (refer to figure 3).
fig. 3 Compressions and rarefactions
Compressions are regions with high air
pressure, while rarefactions are regions with low air pressure. (Hass, J.). This is the way
energy travels as a sound wave. The wavelength of sound is the distance from the
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centerline of one compression to that of an adjacent one, or from the centerline of one
rarefaction to that of an adjacent one. The repeating pattern of high pressure and low
pressure regions within the medium is what makes sound a pressure wave and not a
transverse wave. (Physicsclassroom). The amplitude of a sound wave is the displacement
distance of a single particle leftward and rightward once the energy transmittance hits it.
(Britannica). The intensity of the wave depends mainly on the amplitude and the
listener’s proximity to the source. As the energy travels within the medium, it dissipates
gradually, thus reducing the intensity of the sound until it eventually dies off and cannot
be heard over long distances. (Physicsclassroom). To sum it all up, a sound wave is a
mechanical, longitudinal pressure wave that propagates energy with the help of
compressions and rarefactions.
6.4 Sources of Sound
In our everyday lives we hear sounds from countless sources located within our
vicinity. The sounds that are unpleasant, distracting, or irritable are called noise. Anything
that creates noise sooner or later will become an annoyance and a solution for either
removal of the source or attenuating it will be sought out. Such irritations are what the
term noise pollution was introduced for. Sound becomes unwanted when it either
interferes with activities such as sleeping and conversing, or it diminishes one’s quality of
life. (Epa). With the constant progression in technology, travel, and industrialization, noise
pollution increasingly becomes more and more abundant in urban places. Loud speakers,
construction works, transportation on a busy street, air travel, lawn mowers, even simple
household items like a vacuum cleaner or a food mixer are all factors that produce
unwanted and disturbing sound. (Eschooltoday). Humans themselves can be a source of
sound (both wanted and unwanted). The vibration of the vocal cords under air pressure,
as well as the different mouth shapes can create an impressive range of sounds that can
be heard by others. (Barett, J.). Insects produce noise by rubbing their legs, wings, or
other organs. This act of squeezing and rubbing body parts turns mechanical energy in
sound. (Barett, J.).
Depending on the medium and the source of the disturbance, sound transmission
can either be classified as impact sound or airborne sound. Impact sound arises from the
mechanical hit on a surface or a component by an object. Typical sources are footsteps,
jumping, dropping objects, etc. (Gypsumsolutions). Such sounds easily travel through a
building’s construction components – walls, ceilings and floors, since the rigidity (high
elasticity) of those components conducts the sound waves better, as previously
explained, and energy does not dissipate as quickly. Airborne sound sources are speech,
music speakers and other household appliances. (Gypsumsolutions). The vibrations
travelling through the air medium eventually reach a rigid component and begin
transmitting the energy through the construction. However, a greater amount of energy
is lost before it reaches the building component. Therefore the sound travelling through
the constructions is not as intense. (Gypsumsolutions).
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6.5 Room Modes
As stated in section 6.2 Terminology of this report, room modes are the response
of a room to different frequencies caused by sound bouncing off the walls. Depending on
the shape and size of the room, certain frequencies can be significantly boosted, while
other can be dampened. (Gikacoustics). Now that is clear that airborne sound eventually
makes building construction vibrate once the wave reaches it, it will be easier to
understand what room modes really are. If an amplified bass sound is played within a
room and a bass run up the scale is performed, some notes cause the room to resonate
heavily, thus reinforcing the sound. (Aes). These resonance frequencies are mostly
noticeable below 300Hz and can reach as high as 10dB levels. In effect, the resonance
frequencies are the room modes. (Aes). Room modes occur in physical patterns that are
known as standing waves. Those waves
are uneven sound-level distributions
caused by the waves constantly
reinforcing themselves by bouncing off
walls, ceiling, and floor constructions.
fig. 4 The three types of room modes
(Aes). There are three types of modes in
a room – axial, tangential, and oblique. (Sengpielaudio). Axial modes are the simplest.
They are a round trip of the sound wave between two opposing surfaces (for example,
two opposing walls, or floor and ceiling). (Artsites). The fundamental frequency which will
be boosted in a room with regards to the axial modes can be calculated using the formula
ƒ = c/d, where c is speed of sound and d is twice the distance between the opposing
surfaces (remember – it is the round trip that is calculated). Therefore a room with the
height of 3 meters will have an axial fundamental room mode between the floor and
ceiling at ƒ = 343m/s / 6m equalling 57Hz. (Artsites). Since axial modes are the strongest
with regards to sound augmentation within a room, calculating only those could be
sufficient in some cases. The formulas for the other two types will not be included, since
they are not as important to the aims of this report. Tangential room modes include
sound bouncing off 4 surfaces within a room. (Artsites). Oblique modes involve all six
surfaces within a room. (Artsites). Eventually, a formula
for calculating the room
resonance combining all
fig. 5 Room modes formula
three room modes is
compiled. The formula is shown in figure 5. (Artsites). In
the aforementioned formula, L stands for the length of the
room, W is the width of the room, H is the height of the
room, c is the speed of sound in the respective medium
(air), while p, q, and r stand for wave numbers for the
respective three modes (axial, tangential, and oblique).
(Artsites). The values for p, q, and r can be taken from the
fig. 6 p, q, r values table
table shown in figure 6. Usually, for a thorough
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Ivan Donchev
calculation, all possible combinations of values for p, q, and r up to 4, 4, 4 can be used,
however it is not necessary to do so. (Artsites). Several websites on the internet offer free
room mode calculators that use these formulas to provide accurate results, however, in
order to explain the above in an easily understandable way, an example calculation will
follow. Let us assume a simple rectangular room with dimensions of W (width) = 5
meters; H (height) = 3 meters; L (length) = 7 meters; c (speed of sound) = 343 meters per
second. The first mode of the room is when p, q, r are respectively 1, 0, 0. Therefore,
mode 1 equals
√(
)
(
)
(
) → ƒ = 24.5Hz. Using the same formula,
mode 2 equals
√(
)
(
)
(
) → ƒ = 34Hz. Room mode 7, where p, q,
1,
1
and
r
√(
equal
)
1,
(
)
(
would
result
in
a
wave
with
frequency
of
) → ƒ = 71Hz and so on. By following this formula, a
person can calculate as many room modes as needed, using different combinations for
the p, q, and r values. Once sufficient information is gathered (approximately 20 to 30
room modes) it is possible to infer which frequencies will be greatly enforced within a
certain room. An example calculation sheet shown in
figure 7 will be analyzed. In this example, the first mode
of the room is at 37.5Hz, the second is at 57.7Hz and so
on. It is fairly easy to see the fact that with the
increment of each room mode, the frequency of the
respective wave rises as well. Depending on the room
dimensions, the resulting frequencies will vary.
(Sengpielaudio). The table on the right hand side can be
interpreted in the following way. From 90Hz upward,
the room is relatively smooth, with wave frequencies
increasing in a steady fashion with 2 – 4Hz at a time.
(Artsites). This means that the sound produced with this
room will be perceived smoothly by the listener’s ears
after that 90Hz barrier. However, there is a cluster of
frequencies around the 70Hz barrier and a big gap in the
support between 77Hz and 89Hz. (Artsites). This means
that any wave with a frequency close to 70Hz and in
between the 77Hz and 89Hz will be significantly boosted
and will boom out. (Artsites). Therefore, something
absorptive in the construction must be placed in order
to reduce the boosting effect for these frequencies.
(Artsites). This example showed how the results of the
room mode calculations could be interpreted. Following
fig. 7 Example room mode
calculations
the formulae provided above will give a better
understanding of the acoustic properties of rooms.
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Ivan Donchev
6.6 Reverberation Time
When in an enclosed environment, sound can be reflected for a period of time
after the source of emission has stopped producing the energy needed for the vibrations
to occur. This prolongation of sound is known as reverberation and it is abbreviated as
RT60. (Reverberationtime). The time measured in seconds for sound to reach one
millionth of its original intensity (or 60dB) once the source has stopped emitting is known
as reverberation time. (Phydavidson). A space with a long reverberation time is known as
a live environment. (Reverberationtime). Live environments are great for musical venues,
where sound notes can be blended together and enhanced. (Reverberationtime). A dead
environment is one with a short reverberation time and it is best for having conversations
as speech is best understood in such a setting. (Reverberationtime). Table 1 shows the
preferred reverberation times for speech and music alike.
Speech
Music
0.8 – 1.3
Good
Fair - Good
Reverberation time [s]
1.4 – 2.0
2.1 – 3.0
Fair – Poor
Unacceptable
Fair
Poor
Optimum
0.8s – 1.1s
1.2s – 1.4s
Table 1 Reverberation times for speech and music
Reverberation time is affected by two factors – size of the room/space and the
amount of reflective and absorptive surfaces within the room/space.
(Reverberationtime). A space with a lot of absorptive surface will greatly reduce the
energy of sound, stopping it from bouncing back and forth off walls, floors, and ceilings
and thus reducing the reverberation time. (Reverberationtime). On the other hand, a lot
of reflective surfaces will do exactly the opposite and increase the time it takes for sound
to decay to 60dB. Larger spaces have longer reverberation times since it takes longer for
sound waves to reach certain surfaces, lose energy off them, and decay to 60dB.
Therefore, larger spaces will require more absorptive materials in order to reach the
same reverberation time of a smaller space. (Reverberationtime). Absorptive materials
can be added to construction to reduce both reverberation time and the room modes of
lower frequency waves, thus making the environment more people-friendly and
improving living conditions.
Reverberation time can be calculated within the design stages of any project once
the materials and finishes within a room are known. The most common formula for
calculating this is Sabine’s formula, proposed by the American physicist Wallace Clement
Sabine. (Reverberationtime). The formula is RT60[s] =
, where 0.161 is a
constant number for calculations using the metric system, V stands for the volume of the
room (measured in cubic meters), and A is the room’s effective surface area (measured in
square meters). (Phydavidson). The room’s effective surface area is the sum of the
product of an area covered by a particular material and the material’s absorption
coefficient. (Phydavidson). The formula for the room’s effective surface area is A[m²] =
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24 October 2014
ΣαiAi = α1A1 + α2A2 + α3A3 +…. (Phydavidson). The units of αA are sabins. (Phydavidson).
The A in the previous equation is the area of a surface covered in a material that has a
certain absorptive coefficient – α. (Phydavidson). This coefficient characterizes how much
sound is absorbed upon the sound waves hitting the material. (Bembook). The coefficient
ranges from 0 to 1 and a higher coefficient implies better absorption properties.
(Bembook). The absorption coefficient of the surfaces represents how much energy is
turned into heat inside the material. (Bembook). When sound waves strike a surface, a
certain amount of energy will be transferred into the material as heat by either friction or
resonance. (Bembook). When a material has a coefficient of 1 – no sound is reflected and
all of the energy is transformed into heat, on the other hand, if a material has a
coefficient of 0 – no energy is turned into heat and all of the sound is reflected back.
(Bembook). In laboratory conditions, the absorption coefficient is calculated as (absorbed
energy)/(total incident energy). (Bembook). The coefficient is highly dependent on the
wave frequency of sound. Different materials absorb different amounts of sound under
different frequencies. The most often used frequencies for calculations are the 125Hz,
250Hz, 500Hz, 1000Hz, 2000Hz, 4000Hz. (Bembook). Sabine’s formula for reverberation
time deals mostly with higher frequency sounds, whereas room modes calculations deal
with lower frequency sounds. Appendix A shows the absorption coefficients of different
materials for different wave frequencies.
An example calculation using Sabine’s formula can be performed for a sample
rectangular room with dimensions 4mx6mx3m (3 meters being the height of the room) at
500Hz wave frequency. The room has tiles on the floor, untreated brick walls, and an
acoustic tile ceiling (suspended in frames). The volume of the room is
. The effective surface of the floor is calculated as
(
)
(
)
. The walls have a value of
(
(
))
(
)
. The ceiling has a value of
. From those three components, the ceiling has the best acoustical
performance, which was to be expected since it was made out of suspended acoustic
tiles. Therefore, a conclusion can be made that the higher the effective surface area, the
better the lower reverberation time will be. The total effective surface area is calculated
as
.
Now that the values for both the volume (72m³) and the total effective surface area
(16,56m²) are known, the reverberation time for the example room can be calculated.
. Therefore, it would take 0.7 seconds for sound to reach one
millionth of its original intensity. This value implies that the room will be pleasant to hold
a conversation in, but not so much for playing music. Let us examine what were to
happen if the acoustic ceiling tiles were to be removed and replaced with ordinary
plaster. The α1A1 and α2A2 values will remain the same. However the α3A3 will change to
(
)
. This will result in a total effective surface area of
. In the
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24 October 2014
end, the reverberation time of our modified room will be
.
This newly achieved time of 2.5 seconds will provide poor conditions for both
conversation and music alike. This example demonstrates how much of an acoustical
effect the choice of wall, or floor, or ceiling finish can have on any room and space. A
room will most of the time have other objects inside like furniture and people. They too
have absorption properties and will change the reverberation times. Communal areas like
staircases, however, will most of the time remain empty of furniture and sound and will
reverberate for longer periods of time if left unchecked. Therefore, absorptive materials
are a good idea to be placed in such areas. Reverberation time is not the only factor to
consider when dealing with soundproofing construction. Attenuating the intensity of
airborne and impact sounds is also important.
6.7 STC Scale
Partitions of all sorts have the ability to block, absorb, or conduct sound waves to
different areas within a building. The amount of energy lost upon hitting a wall for
example is known as Transmission Loss. This energy loss needs to be measured in order to
determine how good of a sound barrier certain constructions are. The STC scale (or the
Sound Transmission Class) is the most commonly used sound reduction measurement.
(Soundproofingcompany). Assuming a sound source produces a 100dB sound in one
room, while only a 60dB sound intensity is measured in an adjacent room, this leads to
the conclusion that 40dB of intensity was lost while sound was travelling through the wall
construction. This Transmission Loss (abbreviated as TL), just like room modes and
reverberation time, is highly dependent on the frequency of the sound waves.
(Soundproofingcompany). A certain construction might provide a 40dB loss with waves of
500Hz frequency, while only 10dB loss with waves of 200Hz frequency. The STC is
calculated by taking the TL over 16 standard frequencies over the range of 125Hz to
4000Hz (similar to the reverberation time standard frequencies) and plotting the results
on a graph, similar to the
one shown on figure 8.
(Soundproofingcompany).
The results on the graph
resemble a curve, which is
compared to standard STC
reference
curves.
(Soundproofingcompany). If
the graph-plotted results
fig. 8 Sample STC graph with plotted curves
resemble a standard STC 40
curve, then the construction in question has a 40dB rating, therefore it is to be expected
that this construction will dampen sound intensity by 40dB in some, if not most, cases.
(Soundproofingcompany). To put things into perspective, a 40dB-rated wall will deafen a
70dB sound (average street noise) from one room, to only 30dB intense sound (the
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24 October 2014
intensity of a quiet conversation) in an adjacent room. Appendix B can be used as a
reference for how different decibel levels are perceived by the human ear and what they
most easily relate to. The performance of different constructions can be compared when
the curves of all of them are plotted on the same graph. Figure 9 represents the results of
two different wall types – one rated as a 32dB wall (blue curve), and one rated as a 42dB
wall (black curve). Both of them have problems dealing with low-frequency noises and
their curves appear similar; however, their ratings differ by 10dB.
(Soundproofingcompany). The reason for this is the fact that the blue-curved wall
expresses difficulties stopping sound near the 125Hz frequency and it is therefore
measured in the STC scale.
(Soundproofingcompany).
The
black-curved
wall
exhibits
difficulties stopping sound near
the 100Hz frequency and
therefore, those results are not
taken into account, since this
frequency is not part of the STC
scale. (Soundproofingcompany).
fig. 9 STC graph comparing two wall constructions
When in the process of designing
a building, it is a good idea to compare the STC curves of different construction buildups.
Even though a certain construction may have a better STC rating, it may not be the most
suitable one for the project in hand. A certain wall may need to block low frequency
sounds, since those are the only frequency sounds to be expected within that area. In
situations like this, knowing how to read an STC curve will be of use.
7. Negative Effects of Noise
Now that we have explored what sound is and how it works, another side of the
sound properties must be observed in order to realize why it needs controlling and
attenuation. This is the negative side of it – noise. Noise is the unwanted sound, the one
that causes disturbance for people. Sound pollution is incorporated into the fabric of
urban life everywhere. The causes of it can be simplified to six different, yet closely
related, categories – industrialization, poor urban planning, social events, transportation,
construction activities, household chores. (Conserveenergyfuture). All of these, no matter
which category a certain noise falls into, can have negative effects on people.
7.1 Hearing Defects
The World Health Organization (henceforth abbreviated WHO) has documented
six categories of adverse effects of noise pollution; hearing defects is one of the most
common results. (Goines & Hagler). Our ears can take in certain decibel levels of sound
without being damaged. Any exposure to sounds with intensity of less than 70dB does
not result in hearing loss, regardless of the duration of exposure. (Medscape). Sounds
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24 October 2014
exceeding 85dB (equivalent to the noise on a heavy traffic street) for the duration of 8
hours or more daily, is considered hazardous. (Goines & Hagler). When it comes to sound
intensities greater than 100dB (for example, the sound produced by a jackhammer or a
snowmobile), the WHO recommends exposure of maximum 4 hours 4 times a year.
(Goines & Hagler). Exposure to noises exceeding the threshold of pain – 140dB (120dB for
children) must be reduced to a minimum, while sound with intensity of 165dB and up will
most likely cause acute cochlear damage in the first milliseconds of exposure. (Goines &
Hagler). The cochlea is a tiny snail-shaped organ within the inner ear and it is the main
organ for hearing. (Advancedbionics). Any damage to the cochlea is likely to produce
permanent hearing loss. (Advancedbionics). A study shows that a third of the participants
working part-time in such environments have permanent hearing loss of more than 30dB.
(Medscape).
7.2 Sleeping Disorders
Exposure to loud noises will most definitely impede a person’s sleeping habits and
may lead to irritation. (Conserveenergyfuture). Without a good night’s sleep, people may
experience fatigue and a big drop in performance levels both at work and in their
personal activities. (Conserveenergyfuture). The primary sleep disturbances are classified
as difficulty falling asleep, frequent awakenings throughout the sleep process, waking up
too early, and alterations in sleep stages and depth. (Goines & Hagler). Once a regular
occurrence, it can lead to mood changes, decrements in performance, increased blood
pressure, increased heart rate, increased pulse amplitude, vasoconstriction, changes in
respiration, cardiac arrhythmias, and increased body movement. (Goines & Hagler).
Environmental noise is one of the major reasons behind sleep deprivation. It is concluded
that continuous sounds that exceed 30dB will be sleep disruptive, while intermittent
noises increase the probability of being prematurely awakened. (Goines & Hagler). Low
frequency sound is more disturbing to the sleep and has significant detrimental effect on
health, even at very low sound intensity levels. (Goines & Hagler).
7.3 Cardiovascular Issues
Several studies suggest that high intensity noise can lead to several cardio-vascular
diseases, including high blood pressure and elevated heart rate that disturbs the blood
flow. (Conserveenergyfuture). It has been concluded that noise can act as a “nonspecific
biologic stressor eliciting reactions that prepare the body for a fight or flight response. For
this reason, noise can trigger both endocrine and autonomic nervous system responses
that affect the cardiovascular system and thus may be a risk factor for cardiovascular
disease”. (Goines & Hagler). These adversities become noticeable under a routine longterm exposure to sound levels exceeding 65dB, or with acute exposure to sound levels
ranging from 80 – 85dB and up. (Goines & Hagler). This exposure to noise triggers nervous
and hormonal responses, which in turn cause temporary increases in blood pressure,
heart rate, and vasoconstriction. (Goines & Hagler). Subjects exposed to occupational or
environmental noise may exhibit elevated heart rate and peripheral resistance, increased
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24 October 2014
blood pressure, increased blood viscosity and levels of blood lipids, shifts in electrolytes,
and increased levels of epinephrine, norepinephrine, and cortisol. (Goines & Hagler).
7.4 Mental Illness
Even though noise pollution is not believed to be the cause of certain mental
illnesses, it greatly accelerates the development of latent mental disorders. (Goines &
Hagler). Noise contributes to the following adversities: anxiety, stress, nervousness,
nausea, headache, emotional instability, argumentativeness, sexual impotence, changes
in mood, increase in social conflicts, neurosis, hysteria, and psychosis. (Goines & Hagler).
Noise levels exceeding 80dB are associated with elevated aggressive behavior. (Goines &
Hagler).
7.5 Impairment of Cognitive Development
Extensive research has been done on the effects of noise on the cognitive functions of
people. (Goines & Hagler). The processes most adversely affected by noise are reading
attention, problem solving, and memory. (Goines & Hagler). With regards to memory,
two types of deficit under noise exposure have been identified while conducting the
research – recall of subject content, and recall of incidental details. (Goines & Hagler). It
has been found that children in noisy environments have heightened sympathetic arousal
caused by increased levels of stress-related hormones and elevated resting blood
pressure. (Goines & Hagler). Those results were observed with children with lower
academic achievements. (Goines & Hagler). It is estimated that 68% of children in the EU
are exposed to safe sound levels of less than 55dB, 19% fall within the 55-65dB, 11%
within the 65-75dB, and 2% are exposed to highly dangerous levels greater than 75dB.
(Theakson, F.). These findings lead to the conclusion that more attention needs to be paid
to the environment in which the youth are learning – both in school and at home. (Goines
& Hagler).
7.6 Annoyance
In this case annoyance caused by exposure to noise is more closely defined as
aversion or distress, since it causes displeasure associated with any factor or condition
believed by a person to adversely affect him or her. (Goines & Hagler). Annoyance is
boosted as a response by low frequency noises and by physically feeling the vibration of
different components by the low frequencies. (Goines & Hagler). Other responses that
are close to the feeling of annoyance include anger, disappointment, dissatisfaction,
withdrawal, helplessness, depression, anxiety, distraction, agitation, or exhaustion.
(Goines & Hagler). Other factors that deepen the response are related to the duration
and intensity, the meaning associated with it, the activity the noise interrupts, the
conviction that third parties are able to keep the noise down, and fear of the noise
source. (Goines & Hagler). Studies have concluded that an average day-night noise levels
in an outdoors residential area are acceptable up to 55dB, while the acceptable average
indoors sound levels are 45dB. (Medscape).
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8. Construction Principles for Sound Attenuation
The following sections in this report strive to find the answers to the main
research purpose of this document – how to stop sound travel through the building.
Regardless of the source, a well-insulated and sound-protected building must be able to
provide the residents with peace and quiet. Within the topics below, information about
sound travel, building regulation demands and construction details and systems can be
found. Now that we are aware of what sound is, how it behaves, and how it can adversely
affect people, it is only fitting to find out how to attenuate it.
8.1 Sound Travel through the Building
Sufficiently intense sound generated in one room or area of the building will
undoubtedly find its way around and spread to adjoining rooms. Before solutions for
sound stoppage can be examined, a constructing architect must be aware of the different
ways in which noise travels from one area to another. The passage of sound from one
area to another is described by the term sound transmission. (Paroc). Transmission of
sound through walls and floors adjacent to the building component locations is known as
direct sound transmission. (Paroc). Direct sound transmission occurs when sound
vibrations travelling through the air medium hit a wall or a floor and in turn that building
component begins vibrating with the same frequency, thus transporting the vibrations to
the other side where the undisturbed air molecules eventually pick up the vibrations
(explained in detail in section 6.4 Sources of Sound). Sound travelling through walls and
floors to areas that are not directly adjacent to the building component is known as
flanking path or flanking noise. (Greengluecompany). When it comes to flanking noise
through the external
wall construction, it is
mostly the inner leaf of
the wall that carries the
vibrations
through.
(Bre). Sound that is
being
transmitted
through the building’s
service pipes is known
as overhearing. (Paroc).
fig. 10 Sound travel through construction
Any
other
sound
transmission through cracks, holes, and gaps within the building is known as leakage
sound. (Paroc). Leakage sound most often travels through gaps for electrical socket
fittings, gaps around doors, keyholes, light switches, pipework penetrations, windows
that are not sealed well, etc. (Level). As explained in section 6.4 Sources of Sound, the
noise decreases in intensity while travelling through the construction since energy is lost.
Figure 8 shows an approximation of how much an 80dB sound is deafened when
travelling through the different sound transmission methods. The red arrow indicates
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24 October 2014
direct sound transmission, blue and green arrows indicate flanking noise, while the
orange arrow shows the overhearing through ducts. It is apparent that noise travels the
easiest through service pipes and arrives the most intense on the other side. Airborne
sound is most easily transmitted through overhearing and direct transmission, but it can
also travel through flanking paths. Impact sound is most often transmitted with direct
transmission and flanking paths. (Bre).
8.2 Basic Construction Treatment Methods
If any of the more advanced construction principles and details are to make sense,
a basic and less specific understanding of sound stoppage is preferable. In order to
minimize the different sources of sound transmission, the room within a room concept
can be implemented. (Greengluecompany). This idea suggests having completely
independent building components (like floors, walls, and ceilings) from the main
construction components. In other words, each room is to have 4 internal and
independent wall constructions that are studded out in such a way as to not be in contact
with the any of the 4 main wall constructions. (Bre). Floors are elevated from the main
slab and sound insulation layers put below, while ceilings are to leave a void between
themselves and the upper level floor slab; in effect not being connected to the slab, but
rather the 4 stud wall constructions. (Bre). The remedial treatment of walls is fairly
simple, but can be very effective. A timber studwork frame is constructed and attached to
both the original ceiling and floor construction, but not to the original wall. (Bre). If there
is even the slightest touch between the new and
original wall constructions, sound will still be able
to travel with direct sound transmission. Mineral
wool has low sound transmission properties due to
low elasticity (explained in section 6.2
Terminology); therefore it is a good idea to be
placed in between the vertical studs. (Bre). Two
layers of plasterboard are to be applied in such a
way as to ensure the joints between the sheets do
not coincide with the layer below (decreases the
fig. 11 Remedial wall treatment
gaps and therefore no leakage sound is present).
(Bre). Finally, the perimeter is sealed with a flexible
sealant. (Bre). Figure 11 illustrates the
aforementioned construction method. This
construction method can be applied to ceilings as
well. Wall plates are attached to the walls and new
timber ceiling joists are laid out at the shortest
room span, attaching them to the wall
construction, but not the original ceiling. (Bre).
fig. 12 Remedial ceiling treatment
Mineral wool is placed between the joists and two
layers of plasterboard are placed in such a way as to minimize cracks and leakage
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24 October 2014
transmission. (Bre). The perimeter is sealed with flexible sealant. (Bre). Figure 12 shows
the independent ceiling construction. If the ceiling cannot be upgraded, a floating floor on
the upper level will be the solution. (Bre). One of the many ways to build a floating floor
(also known as raised access floor) is to remove the existing floor boards and lay
insulation between the existing floor joists. (Bre) Once that is done, another layer of
insulation is laid on top of the joists (note: a density of between 60-80 kg/m³ is required).
(Bre). A layer of loose plasterboard is placed on top and finally the floor finish is glued,
not nailed, to the loose plasterboard. (Bre). A good idea to keep in mind is placing a layer
of flexible foam strip behind and below the skirting boards to reduce the possibility of
flanking sound transmission. (Bre).
Those are the basics of sound attenuation within the building. The following
sections of this report will demonstrate variations and detailed illustrations and
descriptions of those basic methods. The logic behind them is similar if not the same – by
separating constructions from one another, sound vibrations face a considerable
challenge making their way through. Different construction approaches can be
implemented in order to satisfy the respective building regulations.
8.3 Building Regulations Demands
The following is based on information and excerpts taken from the Approved
Document E – Resistance to the Passage of Sound of the 2010 Building Regulations for the
United Kingdom.
The building regulations have separate demands for purpose built dwellings and
those that are formed by a material change of use. A material change of use is explained
as a building that is to undergo a change in the purposes for which or the circumstances
in which this building is used. For example: the building is used as a dwelling, where
previously it was not; or the building contains a flat, where previously it did not, etc. (the
full list can be found on page 9 of the Approved Document E). The performance standards
for separating walls, separating floors, and stairs that have a separating function for
dwelling houses, flats, and rooms for residential purposes are as follows:
Purpose Built
Walls
Floors and Stairs
Change of Use
Walls
Floors and Stairs
Regardless
Internal Walls
Internal Floors
Airborne Sound Insulation min [dB]
Impact Sound Insulation max [dB]
45
45
62
43
43
64
40
40
-
Table 2 UK Building Regulations for sound insulation (Approved Document E, p.12)
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Ivan Donchev
The following is based on information and excerpts taken from the 2010 Building
Regulations issued by the Danish Ministry of Economic and Business Affairs and the
Danish Enterprise and Construction Authority. Excerpts from DS 490 – Sound
Classification in Dwellings, issued by the Danish Building Research Institute are also taken
into account.
The Danish system is slightly different than the UK one. It uses the sound
classification of dwellings stated in the DS 490 document. A dwelling can be class A –
excellent acoustic conditions; class B – clearly better conditions than the minimum; class
C – minimum demand for new built; class D – sound class for older buildings and some
renovation works. The conditions are as follows:
AIRBORNE SOUND
Between dwellings or living rooms
Between a dwelling and outside spaces
Between shared living rooms
Doors between dwellings and common spaces
Class A
min [dB]
Class B
min [dB]
Class C
min [dB]
Class D
min [dB]
68
63
63
32
63
58
58
32
60
55
55
32
50
50
50
27
Table 3 DS 490 sound demands for airborne sound for different dwelling classes
IMPACT SOUND
Living rooms/kitchens from noisy premises
Living rooms/kitchens from other dwellings
Living rooms/kitchens from stairs, WCs, balconies
Living rooms/kitchens from other living rooms
Class A
max [dB]
Class B
max [dB]
Class C
max [dB]
Class D
max [dB]
38
43
48
48
43
48
53
53
48
53
58
58
53
58
63
63
Table 4 DS 490 sound demands for impact sound for different dwelling classes
The differences between the regulations in the two countries are apparent. Danish
regulations are stricter and would require additional sound protection to building
components in order for conditions to be met. Windows and doors should be carefully
selected when designing a building in order to closely match the required decibel values
of other constructions. Both the Danish and the United Kingdom’s Building Regulations
and auxiliary documents provide suggestions and guidelines for windows and doors as
well. Construction principles and details can also be found in the Approved Document E of
the UK’s building regulations, thus making it easier to see which principles might be a
good idea to implement in a project in order to meet the demands.
8.4 Floor Construction Details and Systems
Depending on the budget of a project, several approaches can be taken when it
comes to acoustic treatments to floors. In many cases the client does not have excessive
funds to spend on good quality systems for noise control. Yet, it is still possible to
construct the story partitions in such a way as to meet the building regulations for sound.
As long as the general principles are followed, both the United Kingdom’s and the Danish
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regulations can be met; it is just a matter of figuring out the sufficient thickness of
insulation required.
For example, a fairly inexpensive but effective way to stop sound in the floor is the
principle showed on figure 13. In this case, the main construction consists of hollow-core
pre-cast concrete deck elements. Concrete in
itself can be a very good sound barrier,
provided a thick layer is used. A 200mm thick
hollow-core slab can have an STC rating as
high as 50. (Kerkstra). In order to increase this
rating by just 2 points (to 52), a hollow-core
slab of 300mm will be required (Expocrete).
Solid concrete slabs can reach values of 57dB
and above if they are 250mm thick or more.
(Concretecentre). This, however, leads to very
fig. 13 Resilient layer treatment method
heavy and expensive constructions. An easier
and possibly cheaper way to reach even better STC ratings is to use the “floating floor”
system. A resilient layer of insulation is placed on top of the concrete and, crucially,
lapped near separation walls. This lapping of the insulation can be discretely hidden
under the skirting board that is to be placed afterwards. It helps reducing the flanking
transmission of sound by providing a medium of low elasticity between the sturdier
concrete screed finish, and wooden boards finish that will otherwise be in contact with
the wall and provide an easy bridge for vibrations to travel through. Depending on the
finishes needed, a concrete screed may be cast on top, or other floor finish can be applied
(like wooden boards suspended on battens). This, combined with a further treatment to
the ceiling below can effectively bring the desired 45dB rating for the UK and higher than
50dB ratings to meet the Danish regulations for reduced project costs. This method has
been used in the Framed Residential Development, Sportcity project in Manchester and
has successfully reached a rating of 50dB when tested. (Concretecentre). The Bron Drew
Residential Development in Colwyn Bay has also used this system on a concrete slab only
100mm thick, yet the desired 45dB rating was still achieved. (Concretecetre). It is a
method that can be easily carried out and can be applied to refurbishment works as well.
The concept of a raised access floor, whether it be a pedestal option or a cradle
option is also a viable and affordable choice for both new built and renovation projects.
By elevating the finish floor surface on acoustic pedestals, impact sound transmission
through the floor construction is greatly reduced. With finish floor level heights varying
from about 45mm to about 370mm and load capacity from about 2.0kN to approximately
4.0kN, the raised access floor can be used in both residential and commercial buildings,
providing the necessary heights for all intents and purposes. (Kingspan). The zinc plated
pedestal sits on top of a snap-on flexible polymer-based acoustic pad which separates the
two layers of floor finish from one another, thus providing a sound barrier. (Kingspan).
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24 October 2014
The construction also allows for pipes to run under the raised floor. The acoustic
performance of the pedestal option is compliant with the Building Regulations and
achieves an impact sound transmission rating of 19dB. (Kingspan). Depending on whether
the floor space between the original construction and the finish is left hollow, airborne
sound transmissions may or may not be a factor. If left without any further treatments,
the pedestal floor will not provide sufficient airborne sound insulation to reach the class A
and B of the Danish Building Regulations, but it will still be sufficient to be Part E
compliant. The panels that sit on top of the pedestals are made out of high-density
chipboard, which is an excellent material from environmental point of view, since it is
easily reusable. The thickness of the panels varies, however the one which is most often
used is the 38mm, which has an airborne sound insulation index of 62dB when tested
with a concrete slab floor. (Hyperline). The dimensions of the panels are most often
600x600mm. Additional layers of insulation material can be placed within the void
formed by the pedestals to reach the desired decibel levels for class A and B for the
Danish regulations.
The cradle-type raised access floor has a similar construction principle to the
pedestal option. Timber battens are placed on specially designed cradles which sit on top
of a packer layer similar to the
polymer acoustic pad to provide
impact sound insulation. The
packer layer can either be 10mm or
30mm, while the battens are either
a 43x25mm one, a 43x35mm one,
or a 43x43mm one. (Instacoustic).
fig. 14 Cradle system treatment method
An acoustic insulation quilt is
placed between the cradles, ranging from 60 – 100mm thick. (Instacoustic). Depending on
the timber strength of the battens and their thickness, the cradles can be placed at
300mm, 450mm, or 600mm centers, while batten centers can vary between 300mm,
400mm, or 600mm. (Instacoustic). The panel is either an 18mm or a 22mm chipboard
panel. An optional resilient flanking strip can be hidden under the skirting board to help
reduce flanking transmission. Depending on the construction of the structural floor
below, the acoustic performance of the floor type varies. For a typical timber floor
construction, the airborne sound transmission is 54dB (Part E compliant and class D
compliant) while the impact sound is 50dB. (Instacoustic). For a typical concrete slab
construction, those values are as follows: 56dB for airborne (class C and part E compliant)
and 42dB for impact sound. (Instacoustic). Finish floor level can vary from 63mm to
116mm depending on the batten and cradle packer layer choice. (Instacoustic). The
cradle-based raised access floor provides less maneuverability with regards to finish floor
level height modifications, since the pedestal option is fully adjustable to a desired height.
The pedestals also have a better acoustic performance, especially when it comes to
impact sound transmission. However, the cradles are cheaper and more environmentally
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Ivan Donchev
24 October 2014
friendly, since timber can be easily recycled. Both options satisfy both Danish and British
Building Regulations; however in order to reach class A and class B construction ratings
for the Danish Regulations, further floor treatments or additional ceiling treatments are
required.
For projects where the excessive raise in finish floor level is not a desirable
approach, raised access strategies and the addition of resilient layers beneath the floor
finish cannot be implemented. In situations like this, a further look at the choice of floor
finish will be necessary. A textile floor finish may provide the solution. This special textile
buildup is made out of recycled
PVC backing for a base and nylon
6.6 fibers that are firmly anchored
into
the
base
layer.
(Forboflooring). It is a durable and
easy to install floor covering that
can be purchased in both sheet
and tile formats. (Forboflooring).
fig. 15 Textile carpet treatment method
This option can be exercised in
both new built and renovation projects for both residential and commercial purposes. It
has an impact sound reduction value of 19dB, which compares to the one achieved with
the pedestal solution, without the additional floor height. (Forboflooring). The average
sound absorption coefficient is 0.10. (Forboflooring). If we are to compare this type of
carpet to one that is normally used as a floor finish using Sabine’s formula (discussed in
section 6.6 Reverberation Time) for a 5x5x3m room where the walls and ceiling are a
constant and the sound frequency is 500Hz we will notice that: volume = 5x5x3m = 75m³;
floor/ceiling area = 5x5m = 25m²; wall area = 4x5mx3m= 60m²; ΣSα500 = (25m x 0.10) +
(25m x 0.06) + (60m x 0.08) = 8,8m² for total effective area; Therefore the reverberation
time in a room with the nylon 6.6 carpet will be RT60 =
= 1.4s. On the other
hand the same room with a normal carpet will result in ΣSα500 = (25m x 0.14) + (25m x
0.06) + (60m x 0.08) = 9,8m² and the RT60 =
= 1.2s. Therefore, normal a typical
carpet used in this situation will provide better airborne sound acoustic properties.
Judging by this result, the advantage of the nylon 6.6 carpet is its impact sound reduction.
Therefore, it will be a more useful solution for a project where a lot of impact sound is
expected, yet not so much airborne sound (for example: an office, or a library). Using this
carpet solution in daycare centers, kindergartens, and primary schools will be useful with
regards to the sound children make while running around; however, additional acoustic
treatments will be required to dampen any shouts or screams.
Combination treatment methods can be very useful in projects where high
standard sound rating is needed. Since most construction methods and products on the
market cannot reach the necessary decibel ratings for class A and B of the Danish
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Ivan Donchev
24 October 2014
Regulations, two or more of them may be required in order to achieve those decibel
values. In most buildings in the United Kingdom, a standard story partition is constructed
out of timber joists. This means that in most conversion or renovation projects, there will
be sufficient space for insulation to be placed in between the timber joists in order to
provide improved airborne insulation ratings. In projects where access to the unit/area
below the desired floor for treatment is not possible, the solution can be the one shown
in figure 16. In this case three methods of tackling the problem have been implemented.
Firstly, the existing floor finish has been stripped out and a quilt of soft insulation with a
desired thickness has been placed between
the timber joists. Afterwards, a layer of
chipboard has been placed and on top of it the
cradle system has been applied. A sufficient
layer of insulation is again placed between the
cradles in order to improve the airborne sound
transmission. Finally, an overlay system (a
resilient layer) has been placed on top and the
floor finish put in place. This was a solution
fig. 16 Combination system
used for a conversion project and once
finished and tested on site, the results were an airborne sound rating of 56dB and an
impact sound rating of 53dB. (Instacoustic). With the addition of another layer of soft
insulation in between the existing floor joists, an airborne sound rating satisfying the
conditions for class B of the Danish regulations can easily be achieved, which will be an
achievement considering the nature of the project (renovation). A layer of nylon 6.6
carpet could be placed on top of that as a floor finish in
order to help the impact sound rating, making it four
different systems used in treating this floor. The addition of a
resilient flanking strip next to the wall construction can used
to help flanking sound reduction. Another way of dealing
with flanking sound at a cavity wall construction is placing a
small piece of insulation where the floor meets the wall as
shown on figure 17. This only works if the cavity is not
already insulated for thermal considerations. It is not
necessary to stick to only one treatment method. Combining
different ones will yield better results, but it will also cost
more money and resources. Combination systems are best
fig. 17 Cavity stop
used in high-profile projects that aim to reach the class A and
class B ratings described in the DS 490 document. In most cases, combination systems will
be used in renovation projects where the original construction has little if no acoustic
properties. In new built projects one or maximum two methods can be sufficient.
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Ivan Donchev
24 October 2014
8.5 Wall Construction Details and Systems
When it comes to attenuating sound waves and preventing them passing through
wall constructions, there are several things to consider – the thickness of the wall, the
material buildup of it, the weak points in it (like openings for doors and windows), and
most importantly – the lining system that is to be used in order to achieve a satisfactory
STC rating. Sufficient thickness for most separating masonry walls that lack structural
openings, for example, may be a sufficient solution to the noise problem. The student
accommodation project Pavilion H Howlands Farm for the University of Durham utilized
180mm cast-in-situ concrete separating walls, which once field tested, were given an STC
rating of 48, which complies with United Kingdom’s regulations. (Concretecentre). The
same 180mm cast-in-situ concrete separating wall system was used for the Colman House
student accommodation project for the University of East Anglia and similar results were
achieved – an STC rating of 47. (Concretecentre). Adequate wall thickness on its own can
provide satisfactory results, however it may not be the most efficient system to use.
Further wall treatments and lining systems can be more desirable from the point of view
of cost and STC ratings.
The most commonly used systems for soundproofing walls is the plasterboard
treatments. Depending on the type of plasterboard, the total amount of layers, the
insulation used, and the thickness of the wall construction, different decibel ratings can
be achieved. The following solutions are chosen as examples of systems that meet the
British Building Regulatioins for walls that achieve a decibel rating of no worse than 45dB.




2 layers of 12.5mm plasterboard each side of 70mm Gypframe Acoustuds at
600mm centers and no insulation in cavity for a rating of 47dB (total wall
thickness: 122mm). (Britishgypsum).
1 layer of 15mm SoundBloc plasterboard each side of 70mm Gypframe Acoustuds
at 600mm centers and 3 layers of 25mm insulation in cavity for a rating of 50dB
(total wall thickness: 102mm). (Britishgypsum).
1 layer of 12.5mm SoundBloc plasterboard each side of a 92mm ‘C’ stud section at
600mm centers and 3 layers of 25mm insulation in cavity for a rating of 50dB
(total wall thickness: 119mm). (Britishgypsum).
2 layers of 12.5mm SoundBloc plasterboard each side of 70mm Gypframe
Acoustuds at 600mm centers and no insulation in cavity for a rating of 53dB (total
wall thickness: 122mm). (Britishgypsum).
The slimmest possible solution for a gypsum wall that meets the 45dB requirement
without further treatments is

1 layer of 15mm SoundBloc plasterboard each side of a 48mm ‘C’ stud section at
600mm centers and 1 layer of 25mm insulation in cavity for a rating of 45dB (total
wall thickness: 80mm). (Britishgypsum).
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Ivan Donchev
24 October 2014
When it comes to meeting the Danish Building Regulations, wall thicknesses
increase accordingly. The following solutions are chosen as examples of the slimmest
possible systems that meet the requirements of the four classes of sound performance.




1 layer of 12.5mm SoundBloc plasterboard each side of 70mm Gypframe
Acoustuds at 600mm centers and 50mm layer of insulation in cavity for a Class D
wall and a rating of 50dB (total wall thickness: 97mm). (Britishgypsum).
2 layers of 12.5mm SoundBloc plasterboard each side of 92mm Gypframe
Acoustuds at 600mm centers and 100mm layer of insulation in cavity for a Class C
wall and a rating of 60dB (total wall thickness: 144mm). (Britishgypsum).
2 layers of 15mm SoundBloc plasterboard each side of 146mm Gypframe
Acoustuds at 600mm centers and 150mm layer of insulation in cavity for a Class B
wall and a rating of 63dB (total wall thickness: 208mm). (Britishgypsum).
2 layers of 15mm SoundBloc plasterboard each side of
two 92mm ‘C’ stud sections at 600mm centers with
acoustic braces at 3300mm centers and 100mm layer
of insulation in cavity for a Class A wall and a rating of
69dB (total wall thickness: 300mm). (Britishgypsum).
The system is shown in figure 18.
fig. 18 69dB stud wall
The currently best rated gypsum wall buildup consists of 3 layers of 15mm
SoundBloc plasterboard each side of two 92mm ‘C’ stud sections at 600mm centers with
acoustic braces at 3300mm centers and 5 layers of 100mm stone mineral wool insulation
in cavity for a total wall thickness of 800mm and a rating of 80dB. (Britishgypsum). The
buildup is similar to the one shown in figure 18. To put things into perspective, a wall
constructed using this system will reduce the sound of a Boeing 747 takeoff on one side
of it to the sound intensity produced in a quiet conversation on the other end. The low
frequencies, which are the hardest to attenuate, are still reduced to a minimum. At 63Hz,
the wall has a decibel rating of 51 and at 250Hz achieves a rating of 67dB.
(Britishgypsum). Mostly used in developments of theaters, cinemas, and musical venues,
a wall construction of this sort is not the best solution to a regular residential or
commercial project. One of the previously mentioned buildups will be a better and
cheaper solution which, if needed, can be further upgraded using combination
treatments.
The addition of the green glue (also known as acoustic glue) can improve the STC
rating of a fairly simple wall construction. The green glue uses a polymeric formula that
converts the mechanical energy of sound waves into small amounts of heat.
(Greengluecompany). The compound is applied between two rigid layers of material (for
example plasterboard) and imbedded into the wall construction. (Greengluecompany). A
simple reference wall with an STC rating of 40 can easily be upgraded with green glue and
a layer of plasterboard on one side to achieve a rating of 52, or a layer of plasterboard
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Ivan Donchev
24 October 2014
and green glue on both sides of it to reach a rating of 55. (Greengluecompany). This is an
increase of 15 STC points using this treatment. Another example is a wall buildup of two
15mm layers of plasterboard each side of a metal ‘C’ section and insulation that achieves
an STC rating of 61. (Soundproofingcompany). In this case, if the green glue was to be
applied between the two layers of 15mm plasterboard on each side (the rest of the
construction stays the same), the field test results show a STC rating of 66.
(Soundproofingcompany). This is an increase of 5 STC points. The green glue is best used
in order to improve mediocre walls with ratings of around 30-50dB, as it will be inefficient
in further upgrading high-standard walls due to the fact that such improvements will be
negligible, and the results will not justify the cost. An 80dB wall will be upgraded with
neither 15, nor 5 STC points to a rating of 95 nor 85 regardless of the application of green
glue. The application of the green glue will aid wall constructions to reach class D and C of
the DS 490 document, and will definitely improve existing wall constructions to achieve
the rating of 45dB desired by the British regulations. This product is highly sustainable
and the manufacture process of it results in close to zero waste production.
(Greengluecompany). It is best used in renovation projects where existing walls have a
rather middling STC rating.
No matter what wall system is used, the weakest points in any construction with
regards to blocking sound are the structural openings. Windows and doors significantly
reduce the sound performance of a wall, due to the rigidity of their construction and
small cracks or gaps in the seals around them. A standard dual pane window has an
approximate STC rating of 27. (Jeldwen). This can be a major downgrade factor in the STC
rating of any wall construction. One way of improving the sound rating of a window is to
use a product that has dissimilar pane thicknesses. (Jeldwen). For example, one can be
6mm, while the other can be 8mm thick. This change of thickness allows the window
panes to block sound waves at different frequencies. (Jeldwen). One can be used to block
low frequency waves, while the other high frequency ones. (Jeldwen). By using this
solution, the standard window rating can be boosted to reach 34dB. (Jeldwen). Another
factor to consider is the air gap between the two panes. The more air there is, the better
the window will perform. (Jeldwen). Triple glazed windows tend to have less air between
the panes, and therefore perform just as good as a double pane one with different glass
thicknesses, regardless of the fact that they have three layers of glass to stop the sound
(Jeldwen). The frame of the window is just as important to consider. Aluminum frames
conduct sound well, and should therefore be avoided, while wooded and vinyl frames
perform better. (Jeldwen). Windows with a greater glass-to-frame/sash ratio block sound
better - the slimmer the frame and sash, the greater the STC rating. (Jeldwen). As a result,
casement, awnings, and fixed windows perform well due to the smaller frame area and
the air-tightness of their seals. (Jeldwen). Such windows have an approximate rating of
34dB. (Jeldwen). However, there are solutions to choose from for projects where an even
higher STC rating is required. Windows of up to 59dB are available. (Acousticalsurfaces).
Figure 19 shows some of the products and their STC ratings accordingly. 2 panes of
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Ivan Donchev
24 October 2014
fig. 19 High-performance acoustic windows
6.5mm laminated glass with an air gap between them of 13mm in a 115mm aluminum
frame placed in acoustical cores provide an STC rating of 45. (Acousticalsurfaces). The
glass is angled in order to achieve a better rating. Angling the panes has no effect on the
sound insulation properties of the glass. (Audiomasterclass). Flat surfaces cause strong
reflections of sound waves that are not easily dispersed, and thus the reverberation time
is increased. (Audiomasterclass). By angling the glass, however, the sound waves are
reflected towards a surface that has a high absorption coefficient (like a carpet on the
floor, or an acoustic pane in the ceiling), and this surface attenuates the sound waves.
(Audiomasterclass). A combination between a straight glass pane and an angled one is
also possible. An addition of a 9.5mm straight laminated glass to the aforementioned
system will increase the STC rating from 45 to 56. (Acousticalsurfaces). At the same time,
increasing the air space between the panes to more than 250mm will result in a window
with a 59dB rating. (Acousticalsurfaces). Products of this range are most widely used in
recording studios, commercial and industrial projects, military projects, and interrogation
rooms. (Acousticalsurfaces). Using them in residential projects may be considered
overkill. For residential projects, the dissimilar thickness, double pane option with
sufficient air gap will provide satisfactory results.
Similar factors affect door openings as well. Weak frame seals and insufficient
thickness of the door panel will result in poor decibel ratings. There are high-end acoustic
doors available, which provide STC ratings from 47 up to 70. (Iacacoustics). Developed
with special self-aligning magnetic acoustic seals, such products provide no gaps for
sound to travel through once the door is closed. (Iacacoustics). The rating of the door
depends greatly on the materials used and the thickness of the panel. Typically, an 80mm
thick panel will have a rating of approximately 50dB. (Hansengroup). Doors that have no
vision panels in them will perform better with regards to sound, due to the fact that there
are no weak points in the panel. Glass does not absorb sound as well as the rest of the
panel; therefore, if a door is in need of a high sound rating, a plain panel door is certainly
a better solution. If designed properly, doors will have less of an impact to the sound
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Ivan Donchev
24 October 2014
rating of a wall than windows. In any case, the smaller the structural opening is, the
better the overall performance of the wall will be. Therefore, it is always a good idea to
plan the sound performance of a wall considering all the factors that will affect it, rather
than just taking the actual buildup of it into consideration.
9. Conclusion
The problem with noise pollution can easily be tackled and diminished if
constructing architects have the technical and theoretical knowledge of the problem at
hand. The better the understanding and background of an issue, the quicker the solution
can be found. This report found answers to all the questions raised at the beginning, and
the information gathered is essential to the design process of sound attenuation in any
project. The characteristics and the behavior of sound have been explained in an attempt
to make the building solutions and construction details more intelligible and coherent. It
is important to know how and why a certain building principle works, how it compares to
others, and whether or not it is the best suited approach. The familiarity with
mathematical and physical formulas for calculating reverberation times and room modes,
as well as plotting and reading STC graphs is important for constructing architects, since
our career choice requires not only artistic and design-based knowledge, but a technical
background as well. Having careful consideration of the needs of the building’s occupants
is just as vital. The information gathered with regards to all the adverse effects of noise
pollution on any potential inhabitants makes it easier to sympathize with them and be
more respectful with our design methods and attitudes. It is fairly simple to disregard a
certain problem due to the lack of information on the matter. However, when a sturdy
awareness of the basics is achieved and the need for undertaking action is clearly
understood, only then can a competent decision be made with regards to construction
principles. Many, if not all, of these proposed principles can be applied in new-built
projects, renovation projects, and change of use ones. Having the Building Regulations to
back up the undertaken resolution to noise pollution can convince clients that such a
construction is indeed needed. All of the researched construction details in this report
have been applied in numerous projects; while some of them will be and already have
been implemented in developments by the architectural company I am currently working
for. Several of my finds within this report have been considered and applied to future
schemes. All of them are solutions that are practical, applicable, and work in the real
world of construction.
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Ivan Donchev
24 October 2014
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[Accessed 13 October 2014].
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[Accessed 13 October 2014].
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Available at: http://www.physicsclassroom.com/class/sound/Lesson-2/Intensity-and-the-DecibelScale
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[Accessed 13 October 2014].
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24 October 2014
Table of Contents – Appendices
Appendix A – Absorption Coefficients of Materials Table
Appendix B – Decibel Scale
39
Ivan Donchev
24 October 2014
Appendix A – Absorption Coefficients of Materials Table
Material
Acoustic Tile (Suspended in Frames)
Brick
Carpet
Concrete
Concrete Block
Doors (Solid Wood Panel)
Drapery 50% Pleated
Fiberglass Board 25mm
Fiberglass Board 50mm
Fiberglass Board 75mm
Fiberglass Board 100mm
Glass 6.5mm
Marble
Metal Deck 75mm Batts
People Adults (per 1/10 person)
People Teenage (per 1/10 person)
People Children (per 1/10 person)
Plaster on Lath
Plaster on Masonry
Plasterboard 12.5mm on Studs
Plasterboard 12.5mm Susp. Ceiling
Plywood 10mm
Plywood 19mm
Seats (Upholstered Fabric) Empty
Seats (Upholstered Fabric) Occupied
Splayed Cellulose Fiber 25mm
Splayed Cellulose Fiber 75mm
Tile Ceramic
Vinyl/Linoleum on Concrete
Water or Ice
Wood Flooring on Concrete
Wood Flooring on Timber Joists
125Hz 250Hz 500Hz 1kHz
0.5
0.7
0.6
0.7
0.03
0.03
0.03
0.04
0.01
0.02
0.06
0.15
0.01
0.02
0.04
0.06
0.36
0.44
0.31
0.29
0.01
0.07
0.05
0.04
0.14
0.35
0.53
0.75
0.06
0.2
0.65
0.9
0.18
0.76
0.99
0.99
0.53
0.99
0.99
0.99
0.99
0.99
0.99
0.99
0.18
0.06
0.04
0.03
0.01
0.01
0.01
0.01
0.73
0.99
0.99
0.89
0.25
0.35
0.42
0.46
0.22
0.3
0.38
0.42
0.18
0.23
0.28
0.32
0.14
0.1
0.06
0.05
0.01
0.02
0.02 0.03
0.29
0.1
0.06
0.05
0.15
0.11
0.04
0.04
0.28
0.22
0.17
0.09
0.2
0.18
0.15
0.12
0.46
0.66
0.8
0.88
0.6
0.74
0.88
0.96
0.47
0.9
1.1
1.03
0.7
0.95
1
0.85
0.01
0.01
0.015
0.02
0.02
0.03
0.03
0.03
0.008 0.008 0.013 0.015
0.04
0.04
0.07
0.06
0.15
0.11
0.1
0.07
2kHz
0.7
0.05
0.25
0.08
0.39
0.04
0.7
0.95
0.99
0.99
0.99
0.02
0.02
0.52
0.5
0.45
0.35
0.04
0.04
0.04
0.07
0.1
0.1
0.82
0.93
1.05
0.85
0.02
0.03
0.02
0.06
0.06
4kHz
0.5
0.07
0.45
0.1
0.25
0.04
0.6
0.98
0.99
0.99
0.97
0.02
0.02
0.31
0.5
0.45
0.35
0.04
0.05
0.04
0.08
0.11
0.1
0.7
0.85
1.03
0.9
0.02
0.02
0.025
0.07
0.07
References
<http://www.phy.davidson.edu/fachome/dmb/py115/ReverbCalc.html >
<http://www.bembook.ibpsa.us/index.php?title=Absorption_Coefficient>
<http://www.sae.edu/reference_material/pages/Coefficient%20Chart.htm>
40
24 October 2014
Ivan Donchev
Appendix B – Decibel Scale
Decibel Level [dB]
Compares to
0
30
60
80
85
90
95
95
98
100
107
110
115
120
125
125
140
150
155
160
165
170
180
188
210
235
315
Weakest sound heard
A whisper
Normal conversation
Telephone dial tone
City traffic
Truck traffic
Subway train
Threshold of hearing loss
Hand drill
Motorcycle
Power mower
Power saw
Loud rock concert
Boeing 747 takeoff
Threshold of pain
Pneumatic riveter
Jet engine at 200m
Fireworks in close proximity
Gunfire in close proximity
Dragster car
12 gauge shotgun blast
Space shuttle launch
Death of hearing tissue
Blue whale screech
1 ton TNT bomb explosion
5.0 Richter earthquake epicenter
Loudest sound in history –
Tunguska meteor impact
Time until hearing
loss occurs
8hrs
4hrs
2hrs
30min
15min
7min 30s
3min 45s
1min 55s
1min
40s
25s
instant
instant
instant
instant
instant
instant
instant
instant
instant
instant/death
instant/death
instant/death
Note: Due to the intensity of the vibrations that certain decibel ratings achieve, death
is also a possible outcome since the human body will be torn apart. (Listverse).
References
<http://www.gcaudio.com/resources/howtos/loudness.html>
<http://listverse.com/2007/11/30/top-10-loudest-noises/>
<http://zidbits.com/2011/05/whats-the-loudest-sound-and-how-is-it-measured/>
41