VOLUME 2 - SPECIALIST STUDIES
APPENDIX F
6.0
6.1
NOISE
Jongens, Keet Associates (2005) Specialist Scoping Study into
the impacts of noise from the proposed extension on Namakwa
Sands Mine
November 2010
Report No. 6987
JKA
JONGENS KEET ASSOCIATES
ACOUSTICAL ENGINEERING CONSULTANTS
Telephone: 021 – 7945643
A.W.D. Jongens
8 Wingerd Avenue
7806 CONSTANTIA
Tel/Fax: 021 794 5643
Facsimile: 021 – 7945643
email: [email protected]
D. Cosijn
207 Albert Street
0181 WATERKLOOF
Tel/Fax: 012 460 4481
Dr. W. de V. Keet
P.O. Box 236
7440 KERNKRAG
Tel/Fax: 021 553 2331
Architectural Acoustics Noise & Vibration Control Environmental Noise Traffic Noise Acoustical Material Research Underwater Sound Nonlinear Acoustics
SPECIALIST SCOPING STUDY INTO
THE IMPACT OF NOISE FROM THE
PROPOSED EXTENSION OF NAMAKWA SANDS MINE
Prepared for
GOLDER ASSOCIATES AFRICA (Pty) Ltd
August 2005
EXECUTIVE SUMMARY
An initial investigation was conducted into the potential impact of noise due to the proposed
expansion of the Namakwa Sands mine site at Brand se Baai on surrounding land.
The proposed extension to the mine area is bounded by farmland excepting for a stretch of
coastline in the west that includes the beach at Brand se Baai.
It was identified that the primary sources of noise on the mine site that might impact on
surrounding land consisted of large earth moving machinery.
The minimum separation distances required between typical mining operations and the
boundary with adjacent farmland in order to ensure insignificant acoustical impact on the
farmland were calculated.
TABLE OF CONTENTS
1.
INTRODUCTION ............................................................................................................ 1
1.1.
1.2.
BACKGROUND AND BRIEF ............................................................................................ 1
STUDY AREA ............................................................................................................... 1
2.
STUDY APPROACH....................................................................................................... 1
3.
NOISE SENSITIVE AREAS........................................................................................... 3
4.
ACCEPTABLE NOISE LEVELS AND LEGISLATION............................................ 3
5.
IDENTIFICATION OF NOISE SOURCES .................................................................. 5
6.
MEASUREMENT OF NOISE EMANATING FROM MINING OPERATIONS .... 7
6.1.
6.2.
6.3.
6.4.
CATERPILLAR D11R TRACK DOZER............................................................................. 8
KOMATSU WA800 FRONT-END LOADER AND CATERPILLAR 777D TRUCK.................. 9
CATERPILLAR 5130B EXCAVATOR AND CATERPILLAR 777D TRUCK ........................ 10
KOMATSU HM400 ARTICULATED DUMP TRUCKS ...................................................... 11
7.
CALCULATION OF RATING LEVELS OF NOISE................................................ 12
8.
ASSESSMENT................................................................................................................ 12
8.1.
8.2.
9.
NOISE EMISSIONS ....................................................................................................... 12
COMPLIANCE WITH ACCEPTABLE RATING LEVELS OF NOISE ...................................... 13
RECOMMENDED NOISE MITIGATION PROCEDURES .................................... 14
APPENDIX A ......................................................................................................................... 15
JKA
JONGENS KEET ASSOCIATES
ACOUSTICAL ENGINEERING CONSULTANTS
Telephone: 021 – 7945643
A.W.D. Jongens
8 Wingerd Avenue
7806 CONSTANTIA
Tel/Fax: 021 794 5643
Facsimile: 021 – 7945643
D. Cosijn
207 Albert Street
0181 WATERKLOOF
Tel/Fax: 012 460 4481
email: [email protected]
Dr. W. de V. Keet
P.O. Box 236
7440 KERNKRAG
Tel/Fax: 021 553 2331
Architectural Acoustics Noise & Vibration Control Environmental Noise Traffic Noise Acoustical Material Research Underwater Sound Nonlinear Acoustics
SPECIALIST SCOPING STUDY INTO THE IMPACT OF NOISE FROM
THE PROPOSED EXTENSION OF NAMAKWA SANDS MINE.
1.
INTRODUCTION
1.1. Background and brief
Jongens Keet Associates was commissioned to undertake a specialist study for soping
purposes into the impact of noise due to the proposed expansion of the Namakwa Sands mine
site at Brand se Baai.
1.2.
Study Area
A plan of the study area is displayed in Figure 1. This shows the existing West and East
mining area as well as the proposed extension of the mining area. The mine area is bounded
by farmland excepting for the coast in the west.
2.
STUDY APPROACH
An investigation of the acoustical implications of the proposed mine expansion for the
purposes of a scoping report was based upon procedures contained Section 6 of the South
African National Standard (SANS) 10328 “Methods for environmental noise impact
assessments”.
Noise impact assessments of industrial activities normally apply to noise sources fixed in
space. The rating levels of noise on noise sensitive areas are calculated and assessed followed
by seeking possible noise mitigation procedures, if applicable.
This procedure is not conducive to the assessment of noise emanating from mining activities
such as Namakwa Sands where the primary sources of noise are not stationary but move about
the mining area.
It was considered more informative to base the present study on determining the minimum
distances required between moving noise sources and receiver locations to ensure compliance
with acceptable rating levels of noise at the receiver location.
1
FIGURE 1
Map showing location of the study area.
The following procedure was followed:
1. The land use and the nearest noise sensitive areas in the vicinity of the mine were
identified;
2
2. The desired rating level of noise at the identified noise sensitive areas was determined in
accordance with SANS 10103, “The measurement and rating of environmental noise with
respect to land use, health, annoyance and to speech communication”;
3. The sources of noise related to the mining operation were identified;
4. Sound measurements were conducted of noise sources relating to the mining operation;
5. The minimum required distances separating mining operations from identified noise
sensitive areas for no noise impact due to mining operations to occur was estimated;
6. The noise impact of mining operations at closer separation distances was estimated;
7. Noise mitigation procedures were identified and the impact of noise upon implementation
of such procedures was estimated;
3.
NOISE SENSITIVE AREAS
The entire land surrounding the mine site was identified as noise sensitive land in terms of
SAN 10328. The mine is bounded by farmland excepting for the coastline along the western
boundary including Brand se Baai.
4.
ACCEPTABLE NOISE LEVELS AND LEGISLATION
Table 2 of SANS 10103 lists acceptable rating levels for noise in various districts. The table is
reproduced hereunder. Definitions of the terminology used in the measurement and
assessment of noise are contained in Appendix A.
SANS 10103, Table 2 – Acceptable rating levels for noise in districts
1
2
3
4
5
6
7
Equivalent continuous rating level (LReq.T) for noise
dBA
Type of district
Outdoors
Indoors, with open windows
Day-night
LR,dna
Day-time
LReq,db
Night-time
LReq,nb
Day-night
LR,dna
Day-time
LReq,db
Night-time
LReq,nb
a) Rural districts
45
45
35
35
35
25
b) Suburban districts with little
road traffic
50
50
40
40
40
30
c) Urban districts
55
55
45
45
45
35
d) Urban districts with some
workshops, with business
premises, and with main
roads
60
60
50
50
50
40
e) Central business districts
65
65
55
55
55
45
f) Industrial districts
70
70
60
60
60
50
RESIDENTIAL DISTRICTS
NON RESIDENTIAL
DISTRICTS
3
In terms of SANS 10103 the farmland is classified as “rural residential” with acceptable
daytime and night time outdoor rating levels of 45 dBA and 35 dBA, respectively. SANS
10103 provides no guidance in determining the type of district and hence the acceptable rating
levels of noise relating to the coastline including the beach at Brand se Baai.
SANS 10103 contains the statement that the acceptable rating levels for ambient noise are
essentially in line with the recommendations of the World Health Organisation (WHO) for
community exposure. The World Bank has adopted the WHO recommendations on maximum
LAeq in residential areas and schools. These recommendations apply to all World Bank Group
funded projects. The assessments of noise impact in accordance with SANS 10103 therefore
embody WHO and World Bank assessments.
4
5.
IDENTIFICATION OF NOISE SOURCES
During a site visit it was identified that the primary sources of noise on the mine site that
might impact on surrounding land consisted of large earth moving machinery.
At the West Mine, a bulldozer was observed breaking through the hard surface layer prior to
either an excavator or front-end loader scooping material at the work face. The material was
loaded into large off highway trucks that transported the material to a mine tip from where it
was transported on a conveyor belt to the primary concentration plant. There was continuous
truck movement with an empty truck arriving at the work face as a full truck departed.
At the East Mine, off highway trucks were loaded with tailings from a load-out bin that was
transported to rehabilitation areas of the mine. As each full truck departed an empty truck
took its place.
Table 1 records the average daily use of all vehicles used at both mine sites during December
2004. It was assumed that this was representative of typical vehicle use throughout the year.
TABLE 1
Average daily vehicle use in month 12 of year 2004
5
The mechanical power rating of the vehicles is recorded in Table 2
TABLE 2
Mechanical power rating of vehicles used at both mine sites
Working Response area
MACHINE MAKE
Machine Type
Machine Model
KW-rating
Mining West
Komatsu
Front End Loader
WA500
235kW
Mining East
Komatsu
Front End Loader
WA600
328kW
Mining East
Komatsu
Front End Loader
WA600
328kW
Mining West
Komatsu
Front End Loader
WA600
328kW
Mining East
Komatsu
Front End Loader
WA600
328kW
Mining East
Komatsu
Front End Loader
WA600
328kW
Mining East
Komatsu
Front End Loader
WA601
328kW
Mining West
Caterpillar
Track Dozer
D10R
493.5kW
Mining West
Caterpillar
Track Dozer
D10R
493.5kW
Mining East
Caterpillar
Track Dozer
D10R
254.5kW
Mining East
Caterpillar
Tyre Dozer
824C
248.5kW
Mining West
Caterpillar
Tyre Dozer
824D
298.5kW
Mining East
Caterpillar
Water Bowser
D400D
313.5kW
Mining West
Caterpillar
Water Bowzer
D400E
364.0kW
Mining West
Komatsu
Water Bowzer
HD325
324.0kW
Mining East
Komatsu
Articulated Diesel Truck
HM400
321.0kW
Mining East
Komatsu
Articulated Dump Truck
HM400
321.0kW
Mining East
Komatsu
Articulated Dump Truck
HM400
321.0kW
Mining East
Komatsu
Articulated Dump Truck
HM400
321.0kW
Mining East
Komatsu
Articulated Dump Truck
HM400
321.0kW
Mining West
Komatsu
Articulated Dump Truck
HM400
321.0kW
Mining West
Komatsu
Articulated Dump Truck
HM400
321.0kW
Mining West
Caterpillar
Track Dozer
D11R
698.5kW
Mining East
Caterpillar
Motor Grader
14G
158.5kW
Mining West
Caterpillar
Motor Grader
14H
171.0kW
Mining West
Caterpillar
Mass Excavator
5130B
642.5kW
Mining West
Caterpillar
Mass Excavator
5130B
642.5kW
Mining West
Caterpillar
Off Highway Truck
777D
746.5kW
Mining West
Caterpillar
Off Highway Truck
777D
746.5kW
Mining West
Caterpillar
Off Highway Truck
777D
746.5kW
Mining West
Caterpillar
Off Highway Truck
777D
746.5kW
Mining West
Caterpillar
Off Highway Truck
777D
746.5kW
Allround
Bell
Articulated Diesel Truck
B20C
298kW
Allround
Caterpillar
TLB
428C
57kW
Mining West
Komatsu
Front End Loader
WA800
603kW
Caterpillar
Front End Loader
IT-14G
67kW
The information in both Tables was provided by Namakwa Sands.
The highlighted vehicles in Table 1 and those in bold lettering in Table 2 indicate the vehicles
of which the noise emission was measured. This is considered in Section 6.
Noise emanating from the primary concentration plant was considered to have an insignificant
influence on land beyond the mine boundary.
6
6.
MEASUREMENT OF NOISE EMANATING FROM MINING OPERATIONS
Sound measurements were conducted in the vicinity of several mining operations.
The equivalent continuous A-weighted sound pressure level together with the 1/3rd octave
frequency band sound pressure level spectrum was recorded at a known distance from each
mining operation using a Larson Davis Type 824 precision integrating sound level meter.
Prior to and after the measurements the calibration of the meter was checked using a Brüel &
Kjaer type 4230 Calibrator. The microphone of the sound level meter was fitted with a
windscreen and located approximately 1,4m above local ground level. From the recorded data
the 1/3rd octave frequency band sound power levels of the emitted sound was calculated.
The subsections that follow contain a description of each mining operation; a photograph of
the mining machinery/vehicles; and a graph of the Linear and A-weighted 1/3rd octave
frequency band Sound Power Levels derived from the measured sound pressure levels. The
overall Linear and A-weighted sound power levels are recorded in the legend of each graph.
The duration of each of the sound measurements was considered long enough to be
representative of continuous operation of each of the mining operations whether during
daytime or night time as defined in SANS 10103.
The Linear Sound Power Levels were used to calculate the rating level of noise at a receiver
location. This is considered in Section 7.
A-weighted sound (pressure or power) levels relate closely to the human’s subjective
response to sound. The A-weighted Sound Power Levels were included in each graph in order
provide an indication of the parts of the frequency spectrum that would be more noticeable to
a listener.
The highlighted vehicles in Table 1 and those in bold lettering in Table 2 record of which
vehicles the noise emissions were measured during normal mining operations. A study of the
Tables indicates that sound measurements were representative of a large percentage of
vehicles used and included those with the highest mechanical power rating. There is a
reasonably close relationship between the mechanical power rating of diesel engines and the
sound power emitted although this is influenced by the intake and exhaust silencers fitted. It
assumes that all engines are properly maintained.
7
6.1. Caterpillar D11R track dozer
The handheld sound level meter was moved parallel to the motion of a Caterpillar D11R track
dozer breaking through the hard surface layer and moving this towards the edge of the work
face before repeating the operation. The perpendicular distance between the sound level meter
and the CAT D11R was maintained at approximately 15m throughout the sound measurement
duration. A photograph of the CAT D11R is shown in Figure 2. The derived Linear and Aweighted Sound Power Levels are recorded in Figure 3.
Photograph of a Caterpillar D11R track dozer
Sound Power Level: Lin, dB & A-wtd, dBA
FIGURE 2
100
80
60
40
20
0
31.5
63
125
250
500
1000
2000
4000
8000
Frequency, Hz
CAT D11 Lin 115dB
FIGURE 3
A-wtd 111dBA
Linear and A-weighted Sound Power Levels of a CAT D11R track dozer
While conducting the sound measurements it was noticed that a considerable amount of noise
was being produced by the interaction of the tracks with the driving mechanism. This
appeared to be significantly greater than could be recollected from previous measurements
conducted on similar vehicles.
8
6.2. Komatsu WA800 front-end loader and Caterpillar 777D truck
The sound level meter was located at a fixed location 44m from a Komatsu WA800 front-end
loader removing material at the work face and loading this into a Caterpillar 777D truck.
Once filled, the truck moved from the work face to a mine tip where it was deposited onto a
conveyor belt. A second Caterpillar 777D truck moved into loading position within half a
minute of the first truck departing. The movement of the arriving and departing trucks was
along a radius of approximately 44m from the measurement location. A photograph of the
Komatsu WA800 and the CAT 777D is shown in Figure 4. The derived Linear and Aweighted Sound Power Levels are recorded in Figure 5.
Komatsu WA800 front-end loader, left & Caterpillar 777D truck right
Sound Power Level: Lin, dB & A-wtd, dBA
FIGURE 4
100
80
60
40
20
0
31.5
63
125
250
500
1000
2000
4000
8000
Frequency, Hz
WA800 Lin 113dB
FIGURE 5
A-wtd 104dBA
Linear and A-weighted Sound Power Levels of a KMATSU WA800 frontend loader and Caterpillar 777D truck
9
6.3. Caterpillar 5130B excavator and Caterpillar 777D truck
The sound level meter was located at a fixed location 28m from a Caterpillar 5130B excavator
removing material at the work face and loading this into a Caterpillar 777D truck. Once filled,
the truck moved from the work face to a mine tip where it was deposited onto a conveyor belt.
A second Caterpillar 777D truck moved into loading position within half a minute of the first
truck departing. The movement of the arriving and departing trucks was along a radius of
approximately 28m from the measurement location. A photograph of the Caterpillar 5130B
and the CAT 777D is shown in Figure 6. The derived Linear and A-weighted Sound Power
Levels are recorded in Figure 7.
Caterpillar 5130B excavator, left & Caterpillar 777D truck, right
Sound Power Level: Lin, dB & A-wtd, dBA
FIGURE 6
100
80
60
40
20
0
31.5
63
125
250
500
1000
2000
4000
8000
Frequency, Hz
CAT 5130B Lin 113dB
FIGURE 7
A-wtd 106dBA
Linear and A-weighted Sound Power Levels of a Caterpillar 5130B
excavator and Caterpillar 777D truck
10
6.4. Komatsu HM400 articulated dump trucks
The sound level meter was located at a fixed location 12m from a Komatsu HM400
articulated dump trucks being loaded with tailings from a load-out bin. As each full truck
departed an empty truck took its place. A photograph of the Komatsu HM400 is shown in
Figure 8. The derived Linear and A-weighted Sound Power Levels are recorded in Figure 9.
Komatsu HM400 articulated dump truck
Sound Power Level: Lin, dB & A-wtd, dBA
FIGURE 8
100
80
60
40
20
0
31.5
63
125
250
500
1000
2000
4000
8000
Frequency, Hz
HM400 Lin 114dB
FIGURE 9
A-wtd 93dBA
Linear and A-weighted Sound Power Levels of Komatsu HM400
articulated dump trucks
11
7.
CALCULATION OF RATING LEVELS OF NOISE
The Linear Sound Power Levels recorded in the graphs in Section 6 were used to calculate the
separation distance required between the noise source(s) and a receiver located at the
boundary with adjacent farmland in order to comply with the acceptable outdoor rating level
of noise of 45dBA and 35dBA during daytime and night time, respectively, in accordance
with SANS 10103. In terms of SANS 10328, under these conditions there would probably be
no significant acoustical impact on farmland beyond the mine boundary.
The calculation procedure was in accordance with SANS 10357, “The calculation of sound
propagation by the Concawe method” that includes geometrical divergence, atmospheric
absorption, meteorological effects, and ground surface effects in the reduction in sound level
with distance for each frequency.
While conducting the sound measurements the noise in each instance was perceived neither to
contain any pure tones nor to be of an impulsive nature. No pure tone or impulse adjustment
was therefore required in the calculation of the separation distances. The rating level, LReq,T,
therefore was equal to the equivalent continuous A-weighted level, LAeq,T, of noise for a given
time period, T, = 16hrs for daytime or T = 8hrs for night time. It was assumed that each
mining activity occurred continuously throughout a 16-hour daytime period and an 8-hour
night time period.
Table 3 records the sound power emissions of the measured noise sources and the minimum
distance required between noise source(s) and adjacent farmland to comply with the
acceptable outdoor rating level of noise of 45dBA during daytime and 35dBA during night
time.
TABLE 3
Sound power emissions and required minimum distances for compliance
with SANS 10103
Sound Power emitted
Source
CAT D11R track dozer
WA 800 front end loader & CAT 777D truck
CAT 5130B excavator & CAT 777D truck
HM 400 articulated dump truck
8.
ASSESSMENT
8.1.
Noise emissions
Linear,
dB
115
113
113
114
A-weighted,
dBA
111
104
106
93
Distance in metres required to
comply with:
Daytime
Night time
45dBA
35dBA
920
2000
465
1110
585
1360
160
455
A study of the sound power levels recorded in Table 3 indicates that:
•
The Linear sound power level of emitted noise was almost the same for the different
sources. The major sound energy radiated was due to the diesel engines occurring at
frequencies below 500 Hz. This can also be observed in the respective graphs. It was
noted that the diesel engines of all the vehicles were adequately silenced.
12
•
The A-weighted sound power level emitted by the Komatsu HM 400 dump trucks was
significantly less than recorded for any of the other sources. The noise emitted by
Caterpillar 777D trucks alone was not measured. However, the subjective impression
gained during sound measurements was that the level of noise emitted by a CAT 777D
truck was similar to that of an HM 400 truck.
It was observed that at the work face the levels of noise emitted by the WA 800 front-end
loader and the CAT 5130B excavator, respectively, were audibly higher than that emitted by
the CAT 777D trucks due to the higher mechanical power required to scoop and load the
sand. It was considered that the values recorded in the second and third row of Table 3 were
primarily due to the front-end loader and excavator.
The Caterpillar D11R track dozer produced the highest A-weighted sound power level.
Although the diesel engine was adequately silenced the primary source of noise above 500Hz
was caused by the interaction (backlash?) between tracks and driving gear. It was questioned
whether this was normal or whether there was significant wear in the mechanism.
8.2.
Compliance with acceptable rating levels of noise
A study of the calculated minimum separation distances during daytime and night time to
comply with the SANS 10103 acceptable rating levels of noise recorded in Table 3 indicates
that, in the absence of the CAT D11R track dozer, the operation of front end loaders and
excavators at the work face during daytime could approach, respectively, between
approximately 460m and 600m from a boundary with an adjacent farm without resulting in a
significant acoustical impact on the farmland. During night time operation the separation
distance would need to increase to between 1110m and 1400m for no significant acoustical
impact to occur.
The calculations indicated that the Komatsu HM 400 and CAT 777D trucks could operate
within 160m and 455m from the boundary during daytime and night time, respectively, for no
significant acoustical impact on adjacent farmland to occur.
Were daytime or night time operations to occur at shorter ranges than indicated, community
response ranging between “sporadic complaints” and “widespread complaints” could be
anticipated. Refer to Table 5 of SANS 10103.
A track dozer is required to break through the surface layer at the work face prior to operation
of front-end loaders and excavators. If the sound levels recorded of the track dozer were
typical for this type of vehicle, the minimum distance between workface and boundary would
need to be increased to 920m during daytime and 2000m during night time. This increased
distance represents a large area of land if applied along the entire boundary with adjacent
farms.
SANS 10103 provides no indication for acceptable rating levels of noise on recreational land
such as along the coast and at Brand se Baai. It might be suggested that the same rating levels
apply as for farmland. However, this would need to be determined by the local authority.
13
9.
RECOMMENDED NOISE MITIGATION PROCEDURES
All vehicles of which sound emissions were recorded operated with properly functioning
silencers fitted to the diesel engines. This included the Caterpillar D11R track dozer. Even
with the relatively large mechanical power produced during normal operation, the engines of
the vehicles were not considered to be unduly “noisy”. It was thus not anticipated that the
noise emissions from the vehicle engines could be meaningfully reduced.
The major source of noise emanating from the Caterpillar D11R track dozer was the driving
mechanism connected to the tracks. It is believed that large clearance between the driving
gears and track resulted in backlash that generated the high levels of noise from this vehicle.
This would need to be confirmed.
It is recommended that the drive mechanism of the Caterpillar D11R track dozer be inspected
to determine whether noise from this source can be significantly reduced. The overall noise
emission from this vehicle will influence the minimum distance to the mine boundary that
mining operations can be conducted without resulting in a significant acoustical impact on
adjacent farmland. The alternative would be to use a bulldozer emitting lower sound levels.
A.W.D. Jongens
August 2005
14
APPENDIX A
Terminology used in the measurement and assessment of Sound
Certain of the terms used in SANS 10103 are listed hereunder. Their meanings are in certain
instances loosely described to facilitate understanding. Formal definitions of these and
additional terms are contained in SANS 10103.
Ambient noise
the totally encompassing sound in a given situation at a given time, and is usually composed
of sound from many sources, both near and far. It includes the noise from the noise source(s)
under investigation.
A-weighted sound pressure level (sound level), LpA
the sound pressure level, in decibels, relative to a reference sound pressure, and incorporating
an electrical filter network in the measuring instrument corresponding with the human ear’s
different sensitivity to sound at different frequencies.
A-weighted sound exposure level, LAE,T
The value of the A-weighted sound pressure level of a single sound exposure that, within a
reference time interval T, of one second, has the same mean-square sound pressure as a sound
under consideration whose sound pressure level varies with time.
Equivalent continuous A-weighted sound pressure level, LAeq,T.
A formal definition is contained in SANS 10103. The term “equivalent continuous” may be
understood to mean the “average” A-weighted sound level measured continuously, or
calculated, over a period of time, T.
Equivalent continuous rating level, LReq,T
the equivalent continuous A-weighted sound pressure level, LAeq,T, measured or calculated
during a specified time interval, to which is added adjustments for tonal character,
impulsiveness of the sound and the time of day.
An adjustment of 5 dB is added for any tonal character, if present. If the noise is of an
impulsive nature a further adjustment of either 5 or 12 dB, or a value derived in accordance
with Section 5.1.6.1 of the Standard is added. Where neither is present, the LReq,T is equal to
the LAeq,T.
Reference time interval
The time interval to which an equivalent continuous A-weighted sound pressure level, LAeq,T,
or rating level of noise, LReq,T, is referred. Unless otherwise indicated, the reference time
interval is interpreted as follows:
– Day-time:
06:00 to 22:00
T = 18 hours
– Night-time:
22:00 to 06:00
T = 6 hours
15