1
1
PRELIMINARY CHARACTERIZATION OF ACOUSTIC PATHOLOGIES FROM
THE HOUSING HERITAGE OF THE CITY OF LISBON
Ana Sofia Cardoso Carvalho
DECivil, Instituto Superior Técnico, Av Rovisco Pais, 1, 1049-001 Lisbon, Portugal
June, 2009
_________________________________________________________________________
Abstract
This thesis aims to characterise, in a summarised way, de acoustic performance of the most typical
residential buildings in the city of Lisbon. The main objective is to relate the construction
characteristics of a given type of building and the acoustic pathologies directly observed or
identified by the building occupants.
Thus, seven types of building were defined based on the construction period, from before 1755 up
to today. This classification was used then to analyse 72 buildings, spread over 22 districts of the
city. For each of them, the information obtained from direct visual inspection, questionnaires made
to occupants, and non-standardised measurements of sound pressure levels, was checked.
In spite of the continuous improvement of the construction quality, mainly due to more demanding
regulations, which has been confirmed on site, there are yet significant acoustic pathologies, which
result in a large number of inquired occupants complaining about structure airborne noise.
Based on data from surveys, new acoustic diseases emerge, particularly in newer buildings, so
they should be considered in the future.
Key-words: Building acoustics; Construction characteristics; Acoustic pathologies; Questionnaires.
_________________________________________________________________________
1.
Introduction
1.1
Motivation and objectives
The regulations currently in force try to
restrict the levels of noise in the urban
environment and, from there, defines all the
requirements for sound insulation in new
buildings. The first version of the General
Regulation of Noise only dates from 1987.
For the last decade of the twentieth century
buildings and the ones from the first decade
of the century, the application of these rules
was, in many cases, defective, either by
misinterpretation or by negligence of builders,
or ineffective or nonexistent oversight by
licensing bodies.
This thesis seeks to make a small
contribution to the identification of typical
acoustic conditions of housing buildings in
the city of Lisbon. To make this data
collection have been identified seven
constructive periods and for each of them
has been selected a set of buildings.
Resident surveys were conducted in order to
identify hypothetical sound problems of each
building.
The conclusions derived from the
surveys analysis are a tool to support the
development of projects of intervention in
old buildings and give designers a
"feedback" about the performance of
2
buildings designed in accordance with
acoustics law. This improves the quality of
new projects for new buildings.
1.2
Dissertation’s structure
In Chapter 2 the general concepts related
to the acoustics of buildings are presented in
order to better understand the technical and
scientific aspects referred throughout the
dissertation. These concepts will be needed
to understand the analysis results carried out
and the resulting conclusions.
In Chapter 3 are referred the main
features of the constructive and architectural
housing stock, which is divided into seven
distinct constructive periods, starting in
buildings constructed before 1755 (prepombalinos buildings) and ending in buildings
constructed since 1987.
2.2
The Human Hearing
The sounds detected by the human being, in
a simplified form, are the pressure changes
relative to atmospheric pressure, which can
-5
varies between 2 x 10 (threshold of hearing)
2
and 2 x 10 Pa (threshold of pain). Since the
linear scale of variation in sound pressure is
very extensive, was chosen a logarithmic
scale called decibels (dB), which measures
noise levels, given by
L p = 20 log
p
p0
[dB],
(2.1)
-5
where p0 = 2 x 10 Pa is the reference value
corresponding to the origin of the staircase
decibel [0 dB].
In Chapter 4 are identified constructive
types associated with different times and, for
each of them, some buildings are selected.
The constructive lifting is described, based
on information available at City Hall, on-site
visits and resident surveys, for each building.
The evaluation of building’s possible acoustic
diseases is made, in Chapter 5, essentially
based on the results of surveys and
measurements of support, not standardized,
of noise levels inside and outside of
buildings.
The Chapter 6 provides the conclusions
related to common acoustic diseases to
buildings from the same constructive period
and their presumed causes.
2.
2.1
Basic Concepts of Buildins
Acoustic and Legal
Framework
Introduction
The Buildings Acoustics is the science
which studies the sound, its propagation,
either in fluid or in solid medium, and its
effects in humans [16].
Are defined in this chapter the basic
concepts of buildings acoustics and carried
out the legal framework of the buildings
acoustics, through the description of standard
levels of sound insulation, and subsequently
presenting the regulatory limits to be met by
buildings.
Fig. 1- Distribution of some noise sources
nuisances in the range of audible
range of pressures [19].
The most current sound level is
represented by dB (A), since the curve “A” is
the one that best approximates the human
hearing.
To represent the reaction of human
perceivers to noise exposure during a period
of time is used the equivalent continuous
sound level, LA,eq, which is an average level
in terms of energy, measured using the
sound level meter. The LA,eq level is given by
L A,eq
∑ ∆t i x10
= 10 log
∑ ∆t i
LA
10
[dB(A)], (2.2)
where ti is the duration of each measurement
break [N.11].
2.3
Sound Absorption
The sound absorption reflects the
amount of energy that is not reflected by the
3
surrounding surfaces of the compartments or
the objects present on them [11, 16].
The sound absorption is a measure of
acoustic quality of closed spaces and can be
expressed by the parameter "time of
reverberation," which is defined as the time
elapsing between the moment when it
ceased the operation of a sound source and
the moment when there is a drop in the level
of pressure of 60 dB [16]. The time of
reverberation can be estimated in diffuse
sound fields in which the sound pressure
takes a value approximately constant
throughout the compartment, by the
expression of Sabine [11], given by
Tr =
0,16 V
A
(sec),
(2.3)
2
where A (m ) is the equivalent sound
absorption area of the compartment, which
corresponds in a simplified form, to the area
surrounding the surface of the compartment
that can be considered totally absorbing,
considering the rest of the surrounding area a
fully reflective surface.
2.4
Air Noise Isolation
Air noise is caused by the direct
excitement of air due to sound sources outside
or inside the dwellings (television, radio, etc.
...). This type of noise propagates itself by air
and can be transmitted through the
constructive elements (walls, windows, etc...)
[11, 16].
The marginal transmission is the noise
power that interferes with the structure
radiated by adjacent structures. Due to
marginal transmission (Fig. 2), the adjacent
areas contribute to transmit noise to the local
receiver [11, 16].
The rate of noise reduction of the
building elements for frequencies above the
first resonance frequency of the constructive
element of separation is given , on diffuse
sound fields, for
 S 
 (dB).
R = L p1 − L p 2 + 10 log
(2.4)
 A2 
where: Lp1 (dB) and Lp2 (dB) are the average
levels of sound pressure in the compartments
2
transmitter and receiver, respectively, S (m )
is the area of the separation element
2
between compartments, and A2 (m ) is the
area of the sound absorption receiver
compartment. For these frequencies, the
sound transmission is controlled by the mass,
2
m'' (kg/m ) m of the element of separation,
according to the law of mass.
The coincidence or critical frequency, fc
is the frequency at which the wave motion
has the same frequency, wavelength,
amplitude and speed. For frequencies above
this, the index of noise reduction for normal
incidence of waves under conditions of
standard temperature and pressure can be
approximated by where
 f
R ≈ R 0 + log
 fc

 + 10 log η − 2 (dB). (2.5)


where R0 = 20 log (m’’f) - 43 with m'’ is the
separation element of mass, and σ is the
radiation efficiency of the plate, and η is the
loss factor [11].
In order to classify the building elements
according to their ability to isolate the noise,
a calculation of the single value for evaluating
the sound reduction index (Rw) should be
made, from the spectrum of R in-octave
bands or 1/3-octave. When the index Rw is
measured in situ, it is represented by R'w and
is called corrected index of isolation for air
sounds.
If inclusion of heterogeneities such as
windows, doors, the reducing noise from
construction elements is given by
Rw
−R w , j
n
 S 10 10
∑ i
= −10 log i
S



2
Fig. 2–
Transmission of airborne
through building elements
noise







(dB),
(2.6)
where: Si (m ) is the surface area of the
element i; Rw,i (dB) is the unique value of the
sound reduction index of the element i, and n
is the number of heterogeneity elements of
the constructive solution.
4
Regulatory requirements
The indicator DnT,w characterizes the
sound insulation of the air driving standard,
which should be achieved by the partitioning
of horizontal elements (floors) and vertical
(walls) of the building and relates to R'w
through the expression
 0,32 V 
D nT,w = R' w +10 log

 S 
(dB),
T
L' nT = L p2 − 10 log 2
 T0




(dB),
(2.8)
where Lp2 (dB) is the average sound
pressure transmitted directly to the receiver
compartment or radiated from the adjacent
structures (marginal transmission), as shown
in Figure 3 [N.4].
(2.7)
3
where V (m ) is the volume inside the
concerned enclosure receiver.
The RRAE [N.12] establishes the
following requirements for building elements
from building housing that separate:
•
a fire of rooms or rooms from other fire:
DnT,w ≥ 50 dB;
•
the common case of a building from
room or rooms the of adjacent
dwellings:
DnT,w ≥ 48 dB;
DnT,w ≥ 40 dB (if the sender is a box of
lifts);
DnT,w ≥ 50 dB (if the sender is a
garage);
•
places to trade, industry and service
rooms or areas from adjacent
dwellings: DnT,w ≥ 58 dB.
The sound insulation of walls is
characterized by the indicator D2m,nT,w (dB),
which differs from DnT,w only in evaluating the
noise level of the local transmitter. For walls,
the sound pressure level is recorded at two
meters from the front [N.2, N.10].
2.5
Fig. 3 – Transmission of noise through the impact
of the building elements.
The standard noise level of percussion
can be calculated for diffuse sound fields
from standard sound level of percussion,
based in the expression
L'nT,w = L'nT −10 log(0,032 V ) (dB),
(2.9)
The unique value L'nT,w of the standard
sound level of percussion must be obtained
based on the weight curve indicated in EN
ISO 717-2 [N.7].
Regulatory requirements
Percussion Noise Isolation
The percussion noise is made by
vibrations caused by the constituting
elements of structure and surrounding of
buildings. These vibrations are caused by
numerous sources, for example, the human
locomotion, the falling objects, collapse of the
tubes, the vibration of home appliances. This
type of noise is transported by construction
elements in vibration and is transmitted to
compartments by radiation from walls and
floors [11].
According to RRAE, the index L'nT,w
must be less than 60 dB in the interior of
rooms and areas on residential dwellings.
When the place of issue is used to
commerce,
industry,
services
or
entertainment, the standard sound level of
percussion, inside of rooms or living areas of
fires should be less than or equal to 50 dB
[N.12].
The index of isolation to the sounds of
percussion is the standard sound level
measured in the receiving room with the
percussion machine in operation, which is
given by
3.
3.1
Characterization of buildings
in the city of Lisbon
Introduction
The heritage is a historical reference of
great importance not only a social aspect as
5
well as technical, providing evidence to easily
understand the human capacity to adapt to
the surroundings.
Over thousands of years, housing has
risen from just under the place of true place
of comfort, welfare and recreation. The
demands of living are increasingly stringent,
and by improving the constructive solutions,
there is an attempt to satisfy them fully. In
fact, economic and civilized development and
the consequent process of citizens' rights
awareness lead to an increase in demands
placed on buildings performance by its users.
However, the changes observed in buildings
can arise from other causes.
Buildings constructed between 1755 and
mid-19th century - pombalinos buildings:
characterized by foundations of short wooden
stakes of small diameter, stairs, floors and
wood cover with water-attic or attic, threedimensional structure of wood inside the
buildings (Pombalino cage-structure of
masonry blocks and a regular ceramic stone
arches of appliances, interior walls of
nogging), installation of latrines in the
balconies. The acoustic performance should
be better than the previous season, however,
still insufficient [1, 4, 7, 9, S.3].
In the case of the city, can be identified
some causes for the changes observed in
their buildings over the past four centuries,
for example, the earthquake of 1755, the
European and world wars of the 20th century,
the politics of urban leases, guidance policies
at the urban and social fabric of each season
and technological development [3, 8 S.3].
3.2
Characterization of constructive periods
Based on the constructive and
architectural features, that several buildings
in the city of Lisbon have in common, are
involved in seven different seasons:
Masonry buildings with wooden floors:
•
Buildings built before 1755 – prépombalinos buildings: characterized by
stairs, floors and coverage of wood, thick
exterior walls of masonry, interior walls of
high density or nogging, lots of small
dimensions without sanitary facilities.
These buildings must have an acoustic
performance inadequate [1, 3, S.3].
o
Fig. 4 – Pré-pombalino building: n. 223 - Rua
Vale de Santo António.
o
Fig. 5 – Pombalino building: n. 39 da Rua da
Misericórdia.
•
Buildings constructed since the mid19th century until the end of the
decade of 30 of the 20th century gaioleiros buildings: foundations are
characterized by large-filled with stone
masonry of nuts, stairs, floors and
coverage of wood, simplifying or in some
cases elimination of the Pombalina cage,
facades’ walls made of irregular stone
masonry, brick wall of massive resistance
in the warp and stairwells, interior walls of
nogging, installation of latrines in the
balconies and central or lateral foyers.
They introduced the first regulations at
that time on the water supply and sewage
network. At the end of this season is: the
General
Regulation
of
Urban
Construction-RPEE and Regulation of
Reinforced Concrete-RBA, which led,
eventually, to positive effects at the
acoustic level. The sound quality of these
buildings should be less than the
pombalinos [2, 3, 4, 5, 7, 15, S.3.
6
Buildings of reinforced concrete:
•
o
Fig. 6 – Gaioleiro building: n. 26 da Av.
Duque D’Ávila.
Masonry buildings with reinforced concrete
floors- mixed buildings:
•
Buildings constructed in the decade
of 40 of the 20th century-plate
buildings: characterized by consisting
foundations of massive stone masonry
and mortar cement and sand based on
simple concrete skids, facades and gable
at the beginning of the masonry and
stone season and at the end, reinforced
concrete portic structures filled with
punched clay masonry, nogging replaced
by drilled brick masonry reinforced
concrete floors used in the area of
latrines, interior stairways, balconies,
Veranda, coverage. The use of elevator
installed in the porch post pump ladder
was popularized. During the decade of
40
were
not
implemented
new
regulations
remaining
only
those
published in the decade of 30. It was the
existence of these regulations that
allowed the widespread use of reinforced
concrete, with benefits at the acoustic
level. The transmission of percussion
noise have improved, although slightly,
due to reduced thickness of the plaque
elements [15,18,S.3].
o
Fig. 7 – Plate building: n. 65 da Rua Leite de
Vasconcelos.
Buildings constructed in the 50-60
decades of the 20th century are
characterized by the use of reinforced
concrete from the foundations, through
the structures in porch, the resistant
nucleus, slabs and finally on the roof.
The gable walls are made of resistant
reinforced concrete in some sections,
and double ceramic brick masonry. The
interior walls are made of punched
simple ceramic brick masonry. The
installation of two elevators at the stairs
was developed. In force: the General
Regulation of Urban Buildings-RGEU,
the Rules of the Safety Construction
Against Earthquakes-RSCCS, the Rules
of requests in buildings and Regulation of
Transport of Reinforced Concrete
Buildings-REBA. We can expect that the
buildings from this season represent a
significant qualitative leap forward,
compared to his acoustic performance
[15, S.3].
Fig. 8 – Building constructed in the 50-60 decades
of the 20th century: nº 14 da Av. da
República.
•
Buildings constructed in the 70-80
decades of the 20th century are
characterized by continuing to keep the
elements of high rigidity located in the
area of the stairs box and elevators, and
the resistant reinforced concrete walls in
some sections of warp. The outer and
inner walls are similar to the previous
season with increase in thickness. There
is a trend in the solutions used in slabs
with the emergence of reinforced
concrete: massive slabs and slabs
relaxed. This technology was supported
by the appearance in this season of the
Rules of Safety and Actions-RSA, which
replaced the Rules of the Safety
Construction
against
Earthquakes-
7
RSCCS. Also entered into force of the
Regulation of Reinforced Concrete
Structures and pre-stressed-REBAP and
General Rules on Noise-RGR (1987),
which was at the first time, impose legal
limits to the constructive elements of
sound
insulation.
The
acoustic
performance of buildings built in the 70s
and 80s of the 20th century has not
changed significantly in relation to the
previous season [4, 10, 15, 17, S.3].
Fig. 10 – Building constructed since the
beginning of the 90s of the 20th
century: n.º 45 da Av. Duque D’Ávila.
4.
Fig. 9 – Building constructed in the 70-80
decades of the 20th century: nº 77
da Rua Visconde de Santarém.
•
Buildings constructed since the
beginning of the 90s of the 20th
century are characterized by facade
walls are formed by two pieces of
massive ceramic brick masonry with air
box, filled in part by insulation such as
extruded polystyrene, wool rock and wool
glass. There is a change in the
composition of floors, being introduced
resilient materials such as the rock wool
or glass wool between the coating and
the concrete slab. Two regulations
appeared: Regulation of characteristics
of buildings thermal performanceRCCTE and General Regulation of public
systems and buildings of Water
Distribution and Waste water drainage.
The RGR has a final update in this year,
on June 9, 2008. Analyzing the
characteristics pointed out for this
season, there is a major concern in the
construction of buildings at acoustic
level,
improving
its
performance
[10, S.2].
4.1
Adopted methodology in data
collection
Introduction
The ultimate aim of collecting data in the
field is to identify any acoustic conditions of
the various types of buildings studied. In
order to eliminate as much as possible, the
likelihood of detection of isolated diseases
(which occurs only in one building), I chose to
analyze sets of buildings from the same
constructive period in number no less than
three.
4.2
Selection of buildings to be included in
the study
As several diseases can be linked to the
level of ambient noise and to the exterior of
the building, based on General Regulation of
Noise, two periods of reference have been
divided: day and night. Note that although
this policy to refer to three different periods
(day, evening and night), it was considered,
for simplification, that night includes the
hours of the dusk period (from 20 to 23
hours). The purpose of this consideration is
to link these two reference periods with the
Statement of Noise released by the city of
Lisbon.
In these maps is used as a noise
indicator LA,eq cited in Chapter 2. Two
environmental
noise
indicators
are
considered based on the index LA,eq: Ldia and
Lnoite, defined in the earlier version of RGR
8
[N.14] as an indicator of
daytime
0
noise
and
noise-indicator
of
night,
dB
CLASSIFICATION
OF THE AREA
RANGE
FOR THE
DAY
PERIOD
RANGE
FOR
EVENING
AND NIGHT
PERIOD
Sentive
Area
Litle
Noisy
Area
LA,eq < 55
dB(A)
LA,eq < 45
dB(A)
Mixed
Area
Noisy
Area
55 ≤ LA,eq <
65 dB(A)
45 ≤ LA,eq <
55 dB(A
Área Not
Regulate
Very
Noisy
Area
LA,eq ≥ 65
dB(A)
LA,eq ≥ 55
dB(A)
with the mixed
characterization.
and
sensitive
areas
1500 m
respectively.
Table 1 -characterization of the three intervals
considered
Fig.11- Map with the indicator of daytime noise
[S.4]
Based on the description made in
Chapter 3, I tried to meet each of the
constructive times characterized, a small
sample of at least three buildings for each
range sound, counting a total of 72 buildings.
Through the information provided in
each case existing in the intermediate City
Hall of Lisbon and from a new observation on
the ground for confirmation, a form of
identification and physical and constructive
characterization was produced for all
buildings for further evaluation in terms of
acoustic performance.
dB
0
1500 m
4.3
Fig.12- Map with the noise- indicator of night [S.4]
Through the limits of noise exposure out
in Chapter 3, Article 11 of the previous
version of the General Noise Regulation
[N.14] were set three different intervals of
noise level LA,eq for each period. These
intervals are not regulated and serve only for
the purpose of analysis in this dissertation.
The following table shows the noise level
ranges from LA,eq and its correspondence
Surveys
The users survey is divided into two
major sections: diseases related to air
sounds and the sounds of percussion. The
two types of disease were further divided
based on area or space from sound. For
each type of sound, users were consulted on
the following characteristics of the sound: the
apparent frequency range, apparent intensity,
source, time and duration. It is important to
note that some of these things have great
subjectivity,
so
from
respondent
to
respondent, interpretation may vary.
In order to minimize this subjectivity, to
conduct the survey, there was a concern to
make a brief explanation of the concepts
mentioned therein.
For some of the polled users, acoustic
comfort is still considered a minor problem;
9
even where it was clear the existence of
acoustic diseases. Some users disinterest
also difficult the achievement of reliable
answers. In addition to the surveys, were
also measured the noise levels of internal
and
external
environment.
These
measurements
were
carried
out
expeditiously, with a sound level meter,
QUEST 1800 OB-300 and went towards
achievement of values that would allow a
more reliable characterization of the
environmental sound in place. They were
taken the necessary precautions to minimize
the errors in measurements taken, however,
any rules were followed to carry out the
measurements of noise in the outside and
inside environment.
Despite all these precautions when
carrying out measurements, the results are
only indicative and may include an error not
negligible.
5.
Table 2 - Legend of the answers given
by
respondents
in
the
questionnaires.
The questionnaires results to the seven
constructive seasons that were previously
characterized in Chapter 3, were divided in
two types of sounds: air sounds and sounds
of percussion. For air sounds was still done a
new subdivision by the various forms of
sound
transmission,
which
means,
transmission between compartments of the
same fire, transmission between fires and
transmission between the exterior or
common areas of the building and fire.
Regarding the transmission of noise from
outside or common areas of the building, I
opted to present the results depending on the
type of sound source, considering the road
and air traffic, the permanent noisy activities,
ventilation systems of the building and other
sources mentioned by respondents.
Analysis of Results
5.2
5.1
Introduction
To
facilitate
the
conduct
of
investigations, the user is provided with a
range of possible responses, which are
presented in table 2.
FREQUENCY
RANGE
A
B
High
Low
BA Indistinct
APPARENT
INTENSITY
Fo
Fr
Strong
Weak
M
Médium
MFo Very Strong
MFr
Very Weak
NOISY ACTIVITIES
Sound
Equipment
Drag
AM
Furniture
Engine
CM
Room
Conduct of
CL
garbage
AA
Vo
LH
EI
Voice
Human
Locomotion
Lift
PERIOD
OF OCCUR
D
N
Day
Night
Day and
DN
Night
T Evening
Day and
TN
NIght
PERIOD
UD
Household
Items
C/PS
Gr
Screams
C/PM
PF
Gates of
Fire
C/ND
PP Main Room
QO
TQ
Falling
Objects
PH
MH
Short/Few
Seconds
Short/Few
Minutes
Short/Not
Defined
Few
Hours
Many
Hours
Fall Tubes Const Constant
Vibration from the deck
VP
because of bus passing
VC Coverage fans
•
Air Sounds
Transmission between compartments
of the same place
Since it is assumed that the noise
transmitted from one compartment to the
other within a certain place is directly
controlled by the place users, the RGR does
not impose limits on sound insulation for
walls and floors inside the places. These are
only informational.
•
Transmission between places
•
Transmission between the common
area of the building and place
•
Transmission of external noise - Road
traffic
There was a need to subdivide the
outside noise, since it may have various
origins, from road and air traffic until the
permanent noisy activities such as working in
shops.
It is possible to create a link between the
Statement of noise provided by CML and the
results obtained in the questionnaires and
measurements carried out in several
buildings. Not always the measured noise
levels from the outside are in line with the
10
levels specified in the Statement of Noise,
however, this may be due to the fact that the
measurements were made near the ground.
In Lisbon, as normal, this traffic is more
intense during the day. However, in all
buildings, from all times constructions, the
residents said they realize this type of noise
either during the day or at night.
•
Transmission of external noise - Air
traffic
This traffic only occurs in small spaces of
time, that’s why it is considered of short
duration.
•
Transmission of
Temporary and
activities
external noise permanent noisy
There are activities designated of
temporary noise which become sporadic, like
works of construction and festivities.
All shops, industry and services that
cause a nuisance to all residents of the
surrounding area, are considered permanent
noisy activities.
•
Ventilation systems of the buildings
The ventilation systems of buildings are
referred as a source of noise only in buildings
built from decades of 70-80.
In buildings constructed in prior periods,
ventilation takes place naturally. In most
cases, exhausts of kitchen stove have been
installed, which are not, however, mentioned
as a source of uncomfortable noise.
5.3
Sounds of Percussion
The main sound sources given by the
respondents in this section were the human
locomotion, the furniture dragging and
household utensils. These sources are
momentary, so its duration was classified as
short for all situations.
6.
Conclusion
In
Pre-Pombaline
buildings
was
confirmed poor acoustic insulation of interior
nogging walls and floors of wood, in terms of
air and percussion noise. As expected, the
poor quality of glazing on the facades of
these buildings prejudices the airborne noise
isolation, which has consequences in the
perception of road traffic and other temporary
or permanent noisy outside activities. In PrePombaline buildings, spectral characteristics
were not identified in most of the analyzed
individual situations, which shows the
acoustic performance of buildings throughout
the range of frequencies.
In Pombaline buildings, as expected,
the isolation of the interior walls and floors is
inadequate, allowing the detection of
household appliances operation. There is an
improvement, expected, for the previous
period, demonstrated by the award, the
occupants, which is predominantly low
frequency noise transmitted. As expected,
the introduction of the cage system did not
improve the sound insulation of facades,
which continues to be strongly influenced by
the quality of glazing. The failure of the
airborne noise insulation of the façades still
exists.
In ‘Gaioleiros’ buildings, characterized
by an overall decrease in quality comparing
to the previous period, there is a return to
acoustic performance of Pre-Pombaline
buildings, except in an apparent change in
the behaviour of wood floors, which will be
characterized as more transmitters of low
frequency noise.
In buildings of plate, with the
amendment of the constitution of the interior
walls of wood to simple masonry, it is
confirmed a significant improvement in the air
noise insulation within the fire and between
fires. This improvement of the airborne noise
isolation is observed also between the
common areas of buildings and dwellings. As
expected, the existence of larger voids in
glazed facades has contributed to maintain
the isolation of these at low levels in all
frequency bands, improving the insulation of
impact noise introduced by the appearance
of floors of reinforced concrete, even of small
thickness, is reflected by responses to
surveys, which indicate that addition of the
source of percussion predominantly the
human locomotion, it is still the vibration
induced by operation of elevators in buildings
in which they exist.
In buildings constructed in the
decades of 50-60, is confirmed the
improvement of the insulation of airborne
noise introduced in the previous period with
the interior walls of the brick masonry. The
isolation of the common areas improved in
11
most cases. The widespread use of double
walls of masonry on the facade, in
association with the introduction of better
quality of glazing, did not have the expected
consequences in the improvement of sound
insulation. This may result from increased
spans of glazing and the introduction of
boxes of interior shutters. The insulation
keeps the noise impact of the characteristics
of the previous period, the vibration induced
by operation of elevators and the source of
the noise of predominantly percussion. This
indicates that increasing the thickness of the
floor, in fact, turns its noise performance
better.
The buildings constructed in the
decade of constructive 70-80 show some
diversity, and identified some buildings with
inadequate
sound
insulation
between
dwellings. The insulation of the walls of
separation between dwellings and common
areas of buildings appears, in general,
sufficient, given the absence of complaints
from occupants. The level of insulation of
road traffic noise in front walls is insufficient,
particularly in the lower floors, but
satisfactory in relation to other permanent or
temporary noisy activities outside. The
percussion noise transmitted on fires remains
the apparent low intensity of the average, as
occurred in the previous period. However,
there is no longer a dependency on the
location of the insulation of the building,
which may be due to the majority of buildings
have analyzed coatings of floating floor.
In buildings built from the 90s, with the
first version of the General Regulation of the
Noise in effect, appear the common coated
floating floors, which brought a good
performance in the percussion noise
transmission, which can still be felt in the
range of low frequencies, where these
systems are less efficient. In these buildings,
the air noise isolation is generally sufficient,
both between dwellings and between
dwellings and common areas of buildings
and insufficient facades. In newer buildings,
the collective systems of mechanical
ventilation or air conditioning are becoming
popular, which can cause problems at the
noise level.
Behaviour estimates were verified,
observing improvements in the performance
of the newest buildings, particularly in
buildings constructed from the 90s of the
twentieth century, particularly after January
1988, with the first version of RGR. However,
the sound insulation of walls seems to be a
problem. Simultaneously, it appears to solve
a new problem, which stems from the
proliferation of the mechanical noisy
equipment currently installed in the buildings.
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