aci Acoustical Consultants Inc. To: ATCO Pipelines & Liquids Global Business Unit August 28, Avenue SW Calgary, AB T2R 1L8

Transcription

1 aci Acoustical Consultants Inc Street NW Edmonton, Alberta, Canada T6M 0A8 Phone: (780) To: ATCO Pipelines & Liquids Global Business Unit August 28, Avenue SW Calgary, AB T2R 1L8 Attn: Keith Retzlaff re: ATCO 14 Street SW ATCO Gas Realignment Noise and Vibration Study Dear Keith, Thank you for retaining aci to conduct the noise and vibration study for the ATCO Gas Realignment Project in Calgary, AB. The results and discussion from the noise and vibration monitoring from August 25, 2017 are attached. We trust the information provided is sufficient. Please contact us if you have any questions. Yours very truly, aci Acoustical Consultants Inc., Patrick Froment, B.Sc., B.Ed., P.L.(Eng.) Principal Partner APEGA Permit to Practice # P /28/2017 1

2 1.0 Introduction aci Acoustical Consultants Inc. of Edmonton was retained by ATCO Gas and Pipelines Ltd. (ATCO) to conduct a noise and vibration monitoring for the ATCO Gas Realignment Project (the Project) in Calgary, AB. The purpose of the noise & vibration monitoring was to determine the sound and vibration level contributions at #48 Eagle Ridge Drive SW (the Residential Location). Site work was conducted for aci by P. Froment, B.Sc., B.Ed., P.L.(Eng.) on Friday August 25, Site Location & Project Description As indicated in Figure 1, the Project site is located between the northbound and southbound lanes of 14 Street SW. The site spans from beyond Heritage Drive (south end of the site) to 75 Avenue SW (north end of the site). During the noise and vibration monitoring period the compacting project equipment was located primarily 600 m north of Heritage Drive SW. This placed the equipment approximately m directly east of the rear property line and m east of the residential dwelling at the Residential Location 1. The Project equipment was below the height of the road and surrounded by Jersey barriers on its east and west boundaries. There were breaks in the Jersey barriers along the eastern boundary (adjacent to the northbound lanes of 14 Street SW) which allowed access for the Project equipment. Equipment found on-site during the monitoring period is provided in Table 1. Table 1. Equipment List 2 Type Excavator Loader Packer Rock Trucks Manufacturer & Model Komatsu PC228 Komatsu PC138 John Deer 210CW Cat 938G Vibromax 1103PD (Sheep s Foot) Vibromax 1105D (Smooth Drum) Various Makes and Models 14 Street SW is 6 lane road (3 northbound and 3 southbound lanes, respectively) however, during the monitoring period the northbound direction was reduced to 2 lanes. All 3 southbound lanes were open during the monitoring period. The speed limit spanning from Heritage Drive to 75 Avenue SW was reduced to 50 km/hr. The roadway has noise barriers on either side (along the east and west residential 1 This places the Project equipment as close to the Residential Location as possible during compaction. 2 During the monitoring period the amount of equipment was representative of the work needed to complete the project. Not all equipment on site will be operated simultaneously. 2

3 property lines) that vary in height. Subjectively, the road traffic noise was audible during lulls in construction activity. Topographically, the land immediately adjacent to the Project is flat. Due to the relative distance between the Project and the Residential Location to the west, the vegetative sound absorption is considered negligible. 3.0 Measurement Methods 3.1 Environmental Noise Monitoring The noise monitoring location, as indicated in Figure 1, was conducted at #48 Eagle Ridge Drive SW. The monitor was located approximately 19.5 m west of the rear property line, as shown in Figure 2 & Figure 3 at a height of 1.5 m above ground. At this location, there was no direct line-of-sight to the Project due to the 3.6 m noise barrier found along the rear property line. The noise monitor was started at 09:40 on Friday August 25, 2017 and ran for approximately 3 hours until 13: Environmental Vibration Monitoring The vibration monitor, as indicated in Figure 1, was conducted at #48 Eagle Ridge Drive SW. The vibration monitor was located directly adjacent to the dwelling at the Residential Location, as indicated in Figure 4. The tri-axial accelerometer was mounted at ground level in a small enclosure anchored to the ground and oriented such that the x-axis was parallel 14 Street SW, the y-axis was perpendicular to the 14 Street SW, and the z-axis was vertical. The vibration monitor was started at 09:30 on Friday August 25, 2017 and ran for approximately 3.5 hours until 13:10. Refer to Appendix I for a detailed description of the measurement equipment used, Appendix II for a description of the acoustical terminology, and Appendix III for a list of common noise sources. The noise and vibration measurement instrumentation was calibrated at the start of the measurements and then checked afterwards to ensure that there had been negligible calibration drift over the duration of the measurements. The calibration records can be found in Appendix I. 3

4 4.0 Permissible Sound & Vibration Levels 4.1 Noise Criteria Environmental noise levels from various sources (industrial, roads, railways, etc.) are commonly described in terms of equivalent sound levels or Leq. This is the level of a steady sound having the same acoustic energy, over a given time period, as the fluctuating sound. In addition, this energy averaged level is A weighted to account for the reduced sensitivity of average human hearing to low frequency sounds. These Leq in dba, which are the most common environmental noise measure, are often given for day-time (07:00 to 22:00) LeqDay and night-time (22:00 to 07:00) LeqNight while other criteria use the entire 24-hour period as Leq24. The criterion used to evaluate the noise in the study area is the City of Calgary Bylaw Number 5M2004 (Part 9). The City of Calgary Bylaw Number 5M2004 (Part 9) sets maximum sound levels that may exist between various categories of land use. As indicated in Section 28(1) of the Bylaw, within residential areas, no person shall cause or permit to be caused a Continuous Sound that exceeds 50 dba during the nighttime (22:00-07:00) and 65 dba during the day-time (07:00-22:00). Due to Project activities being limited to daytime hours, the maximum sound levels for the monitoring period are 65 dba. 4

5 4.2 Vibration Guidelines To put the projected vibration levels into perspective, it is necessary to discuss appropriate guidelines and criteria that are accepted for the purpose of evaluating the potential impact of the vibrations. The effect of these vibrations can be evaluated using several different measures that relate to their effect on: a) the structure itself and the potential for damage to it, or b) the individuals using the interior spaces in the structure. With regards to the potential damage to the structure, the common criteria used is from the US Bureau of Mines (USBM) which has extensive measurement and assessment data for blasting and other minerelated construction activities. The document USBM RI-8507 has criteria for the safe levels of impulsive type vibration sources (such as outside machinery) with respect to cosmetic damage to wood framed houses with drywall provided in Appendix IV. The criteria are given in peak particle velocity (PPV) values in mm/s for each 1/3 octave frequency band between 0.8 Hz and 300 Hz. The broadband range of vibration expected in structural response for various sources is also given in Appendix V (from ISO 4886:1990e). Specific to Machinery Outside Ground-borne, the range varies by two orders of magnitude (i.e. from 0.2 mm/s to 50 mm/s). Naturally these levels will depend on the proximity to the source, soil conditions, building construction etc. For a typical residential wood-framed structure, a continuous broadband level with a peak velocity of 70 mm/s is considered safe although minor damage 3 has occurred at half of this level. The criterion for evaluating human response to vibrations is much more complex as it includes exposure time as well as the direction of vibration relative to the position of the body. However, for an undefined axis of vibration, the absolute minimum level at which vibrations can be felt is a peak velocity of 0.14 mm/s with most people having a perception threshold of approximately mm/s. Typically, the vibration becomes strongly perceptible to disturbing at approximately 5-10 mm/s. As a result, unless there is a specific function for the space being considered, this is a reasonable level for short-term vibration without a strong reaction from the individuals using the space being monitored. In summary, the broadband continuous peak velocity criteria used for the protection of structures will be taken as 50 mm/s and the individual 1/3 octave bands will be compared to the USBM RI For human impacts, the level used will be 5-10 mm/s. 3 This includes drywall cracking but no structural compromises of the dwelling. 5

6 5.0 Results and Discussion 5.1 Noise Monitoring Results The results obtained from the 09:50 12:50, August 25, 2017 noise monitoring period are provided in Table 2 and are presented in Figure 5 (isolated, broadband A-weighted Leq sound levels) and Figure 6 (and 1/3 octave band Leq sound levels). The values for this time period are reflective of typical operations of the site which includes time periods in which the compacting equipment is not in operation. The results from the 09:50 10:35 August 25, 2017 noise monitoring period are provided in Table 2 and are illustrated in Figure 5 (isolated, broadband A-weighted Leq sound levels) and Figure 6 (and 1/3 octave band Leq sound levels). The values from this time period are reflective of typical operations of the Project while the compacting equipment is operational throughout. This can be corroborated with Figure 7 of the measured vibration levels which indicates the time periods in which the compacting equipment was not operational. The data was reviewed to isolate (i.e. remove) abnormal noise events. The only event that was removed was a siren that passed by at 11:31. The isolation analysis is consistent with industry standards 4. Table 2. Noise Monitoring Results Time Sound Pressure Level L eq (dba) 09:50-12: :50-10: As indicated in Table 2, the Leq(09:50-12:50) and Leq(09:50-10:35) values for the noise monitoring periods were 59.3 and 60.4 dba, respectively. The 1/3 octave band data, presented in Figure 6, shows the typical trend of low frequency noise (near Hz) resulting from engines and exhaust noise from the site and 14 Street SW and mid-frequency noise (from 315 Hz to 2 khz) from tire noise associated with 14 Street SW. This was confirmed from subjective observations during the setup and take-down of the equipment. As indicated in Table 2, the isolated Leq noise level of 59.3 and 60.4 dba are below the maximum sound level of 65.0 dba thus the noise contributions of the Project are in compliance with the City of Calgary Bylaw Number 5M Example: Alberta Energy Regulator (AER) Directive 038 on Noise Control 6

7 5.2 Vibration Monitoring Results The results of the vibration monitoring can be found in Table 3. In addition, the broadband RMS velocity levels in each of the three vibration measurement directions are provided in Figure 7. Table 3. Vibration Monitoring Results Time Maximum Peak Particle Velocity (mm/s) 09:50 12: The data provided in Figure 7 represents the broadband vibration levels in each of the three measurement axes (horizontal perpendicular to the Project, horizontal parallel to the Project, and vertical) and the vector sum of all three. This vector sum is known as the peak particle velocity (PPV) and is generally the value which is compared to the assessment criteria. Figure 6 illustrates the time periods in which the compacting equipment was not operational (10:40 10:43 & 11:21 12:16). As indicated in Table 3 and in Figure 7, the maximum broadband vibration level measured at the Residential Location was 0.67 mm/s. This is above the absolute minimum level at which vibrations can be felt (0.14 mm/s) and in the range of the perception threshold ( mm/s). However, it is well below the criteria of structural damage of 50 mm/s. Figure 8 provides the 1/3 octave band vibration levels. When comparing the data to the USBM RI-8507 criteria for cosmetic damage for wood framed houses with drywall the monitored vibration levels are well below the criteria at all frequencies, by approximately 1 order of magnitude. Based on the measured broadband and 1/3 octave band vibration levels, it is anticipated that the ground-borne vibration could be perceived at the Residential Location however it is still well below 5-10 mm/s which is a reasonable level for short-term vibration. Lastly, the measured ground-borne vibration levels from the Project equipment are well below the criteria of structural damage of 50 mm/s and thus will not impact the structural integrity of the dwelling at the Residential Location. 7

8 Residential Location Project Equipment Location during Monitoring Period Project Area (Highlighted in Red) 8

9 Figure 1. Study Area 9

10 Microphone (inside windscreen) Project Site Noise Monitor Case Figure 2. Noise Monitor Used for Environmental Noise Study (Facing West) Project Site Microphone (inside windscreen) 3.6 m 19.5 m Noise Monitor Case Figure 3. Noise Monitor Used for Environmental Noise Study (Facing East) 10

11 Accelerometer (within Enclosure) Vibration Monitor Case Project Site Figure 4. Vibration Monitor Used for Environmental Noise Study 11

12 Figure 5. Isolated 15-Second L eq Sound Levels Sound Pressure Level (dba) :50-12:50 09:50-10:35 0 dba dbc Frequency (Hz) 1.25 k 2 k 3.15 k 5 k 8 k 12.5 k Figure 6. 1/3 Octave L eq Sound Levels 12

13 0.70 Horizontal Parallel Horizontal Perpendicular Vertical PPV 0.60 Vibration Velocity (mm/s) :50:00 09:54:00 09:58:00 10:02:00 10:06:00 10:10:00 10:14:00 10:18:00 10:22:00 10:26:00 10:30:00 10:34:00 10:38:00 10:42:00 10:46:00 10:50:00 10:54:00 10:58:00 11:02:00 11:06:00 11:10:00 11:14:00 11:18:00 11:22:00 11:26:00 11:30:00 11:34:00 11:38:00 11:42:00 11:46:00 11:50:00 11:54:00 11:58:00 12:02:00 12:06:00 12:10:00 12:14:00 12:18:00 12:22:00 12:26:00 12:30:00 12:34:00 12:38:00 12:42:00 12:46:00 Time Figure 7. Broadband Vibration Monitoring Results 13

14 0.7 Horizontal Parallel Horizontal Perpendicular Vertical PPV 0.6 Vibration Velocity (mm/s) Hz 1.00Hz 1.25Hz 1.60Hz 2.00Hz 2.50Hz 3.15Hz 4.00Hz 5.00Hz 6.30Hz 8.00Hz 10.0Hz 12.5Hz 16.0Hz 20.0Hz 25.0Hz 31.5Hz 40.0Hz 50.0Hz 63.0Hz 80.0Hz 100.0Hz 125.0Hz 160.0Hz 200.0Hz Time Figure 8. 1/3 Octave Band Vibration Levels 14

15 Appendix I MEASUREMENT EQUIPMENT USED Brüel and Kjær 2250 The environmental noise monitoring equipment used consisted of a Brüel and Kjær Type 2250 Precision Integrating Sound Level Meter enclosed in an environmental case, a tripod, a weather protective microphone hood. The system acquired data in 15-second Leq samples using 1/3 octave band frequency analysis and overall A-weighted and C-weighted sound levels. The sound level meter conforms to Type 1, ANSI S1.4, ANSI S1.43, IEC , IEC 60651, IEC and DIN The 1/3 octave filters conform to S1.11 Type 0-C, and IEC Class 0. The calibrator conforms to IEC 942 and ANSI S1.40. The sound level meter, pre-amplifier and microphone were certified on April 29, and the calibrator (type B&K 4231) was certified on / January 18, 2017 by a NIST NVLAP Accredited Calibration Laboratory for all requirements of ISO 17025: 1999 and relevant requirements of ISO 9002:1994, ISO 9001:2000 and ANSI/NCSL Z540: 1994 Part 1. Simultaneous digital audio was recorded directly on the sound level meter using a 8 khz sample rate for more detailed post-processing analysis. Refer to the next section in the Appendix fora detailed description of the various acoustical descriptive terms used. Record of Calibration Results Description Date Time Pre / Post Calibration Level Calibrator Model Serial Number Noise Monitor 1 August 25, :40 Pre 93.9 dba B&K Noise Monitor 1 August 25, :02 Post 93.8 dba B&K Vibration Monitor August 25, :30 Pre 10.3 mm/s B&K Vibration Monitor August 25, :10 Post 10.4 mm/s B&K

16 B&K 4231 Calibrator Calibration Certificate 16

17 B&K 2250 SLM Calibration Certificate 17

18 B&K 4189 Microphone Calibration Certificate 18

19 SVAN 958 Calibration Certificate 19

20 PCB 356B18 X-Axis Calibration Certificate 20

21 PCB 356B18 Y-Axis Calibration Certificate 21

22 PCB 356B18 Z-Axis Calibration Certificate 22

23 PCB 393C Calibration Certificate 23

24 B&K 4294 Vibration Exciter Calibration Certificate 24

25 Appendix II THE ASSESSMENT OF ENVIRONMENTAL NOISE (GENERAL) Sound Pressure Level Sound pressure is initially measured in Pascal s (Pa). Humans can hear several orders of magnitude in sound pressure levels, so a more convenient scale is used. This scale is known as the decibel (db) scale, named after Alexander Graham Bell (telephone guy). It is a base 10 logarithmic scale. When we measure pressure we typically measure the RMS sound pressure. Where: 2 P RMS SPL = 10 log10 = 20log 2 Pref 10 P P SPL = Sound Pressure Level in db PRMS = Root Mean Square measured pressure (Pa) Pref = Reference sound pressure level (Pref = 2x10-5 Pa = 20 µpa) RMS ref This reference sound pressure level is an internationally agreed upon value. It represents the threshold of human hearing for typical people based on numerous testing. It is possible to have a threshold which is lower than 20 µpa which will result in negative db levels. As such, zero db does not mean there is no sound! In general, a difference of 1 2 db is the threshold for humans to notice that there has been a change in sound level. A difference of 3 db (factor of 2 in acoustical energy) is perceptible and a change of 5 db is strongly perceptible. A change of 10 db is typically considered a factor of 2. This is quite remarkable when considering that 10 db is 10-times the acoustical energy! 25

26 26

27 Frequency The range of frequencies audible to the human ear ranges from approximately 20 Hz to 20 khz. Within this range, the human ear does not hear equally at all frequencies. It is not very sensitive to low frequency sounds, is very sensitive to mid frequency sounds and is slightly less sensitive to high frequency sounds. Due to the large frequency range of human hearing, the entire spectrum is often divided into 31 bands, each known as a 1/3 octave band. The internationally agreed upon center frequencies and upper and lower band limits for the 1/1 (whole octave) and 1/3 octave bands are as follows: Whole Octave 1/3 Octave Lower Band Center Upper Band Lower Band Center Upper Band Limit Frequency Limit Limit Frequency Limit

28 Human hearing is most sensitive at approximately 3500 Hz which corresponds to the ¼ wavelength of the ear canal (approximately 2.5 cm). Because of this range of sensitivity to various frequencies, we typically apply various weighting networks to the broadband measured sound to more appropriately account for the way humans hear. By default, the most common weighting network used is the so-called A-weighting. It can be seen in the figure that the low frequency sounds are reduced significantly with the A-weighting. Combination of Sounds When combining multiple sound sources the general equation is: n = 10log 10 Σ 10 i 1 Σ SPL n = SPL i 10 Examples: - Two sources of 50 db each add together to result in 53 db. - Three sources of 50 db each add together to result in 55 db. - Ten sources of 50 db each add together to result in 60 db. - One source of 50 db added to another source of 40 db results in 50.4 db It can be seen that, if multiple similar sources exist, removing or reducing only one source will have little effect. 28

29 Sound Level Measurements Over the years a number of methods for measuring and describing environmental noise have been developed. The most widely used and accepted is the concept of the Energy Equivalent Sound Level (Leq) which was developed in the US (1970 s) to characterize noise levels near US Air-force bases. This is the level of a steady state sound which, for a given period of time, would contain the same energy as the time varying sound. The concept is that the same amount of annoyance occurs from a sound having a high level for a short period of time as from a sound at a lower level for a longer period of time. The Leq is defined as: L eq db 1 T 1 10 = 10 log dt = 10log 10 T 0 T T P P ref dt We must specify the time period over which to measure the sound. i.e. 1-second, 10-seconds, 15-seconds, 1-minute, 1-day, etc. An L eq is meaningless if there is no time period associated. In general there a few very common Leq sample durations which are used in describing environmental noise measurements. These include: - Leq24 - Measured over a 24-hour period - LeqNight - Measured over the night-time (typically 22:00 07:00) - LeqDay - Measured over the day-time (typically 07:00 22:00) - LDN - Same as Leq24 with a 10 db penalty added to the night-time 29

30 Statistical Descriptor Another method of conveying long term noise levels utilizes statistical descriptors. These are calculated from a cumulative distribution of the sound levels over the entire measurement duration and then determining the sound level at xx % of the time. The most common statistical descriptors are: Lmin L01 L10 L50 L90 L99 Lmax Industrial Noise Control, Lewis Bell, Marcel Dekker, Inc minimum sound level measured - sound level that was exceeded only 1% of the time - sound level that was exceeded only 10% of the time. - Good measure of intermittent or intrusive noise - Good measure of Traffic Noise - sound level that was exceeded 50% of the time (arithmetic average) - Good to compare to Leq to determine steadiness of noise - sound level that was exceeded 90% of the time - Good indicator of typical ambient noise levels - sound level that was exceeded 99% of the time - maximum sound level measured These descriptors can be used to provide a more detailed analysis of the varying noise climate: - If there is a large difference between the Leq and the L50 (Leq can never be any lower than the L50) then it can be surmised that one or more short duration, high level sound(s) occurred during the time period. - If the gap between the L10 and L90 is relatively small (less than dba) then it can be surmised that the noise climate was relatively steady. 30

31 Sound Propagation In order to understand sound propagation, the nature of the source must first be discussed. In general, there are three types of sources. These are known as point, line, and area. This discussion will concentrate on point and line sources since area sources are much more complex and can usually be approximated by point sources at large distances. Point Source As sound radiates from a point source, it dissipates through geometric spreading. The basic relationship between the sound levels at two distances from a point source is: r 2 SPL = 1 SPL2 20log 10 r1 Where: SPL1 = sound pressure level at location 1, SPL2 = sound pressure level at location 2 r1 = distance from source to location 1, r2 = distance from source to location 2 Thus, the reduction in sound pressure level for a point source radiating in a free field is 6 db per doubling of distance. This relationship is independent of reflectivity factors provided they are always present. Note that this only considers geometric spreading and does not take into account atmospheric effects. Point sources still have some physical dimension associated with them, and typically do not radiate sound equally in all directions in all frequencies. The directionality of a source is also highly dependent on frequency. As frequency increases, directionality increases. Examples (note no atmospheric absorption): - A point source measuring 50 db at 100m will be 44 db at 200m. - A point source measuring 50 db at 100m will be 40.5 db at 300m. - A point source measuring 50 db at 100m will be 38 db at 400m. - A point source measuring 50 db at 100m will be 30 db at 1000m. Line Source A line source is similar to a point source in that it dissipates through geometric spreading. The difference is that a line source is equivalent to a long line of many point sources. The basic relationship between the sound levels at two distances from a line source is: SPL 1 SPL 2 = 10 log The difference from the point source is that the 20 term in front of the log is now only 10. Thus, the reduction in sound pressure level for a line source radiating in a free field is 3 db per doubling of distance. Examples (note no atmospheric absorption): - A line source measuring 50 db at 100m will be 47 db at 200m. - A line source measuring 50 db at 100m will be 45 db at 300m. - A line source measuring 50 db at 100m will be 44 db at 400m. - A line source measuring 50 db at 100m will be 40 db at 1000m. 10 r r

32 Atmospheric Absorption As sound transmits through a medium, there is an attenuation (or dissipation of acoustic energy) which can be attributed to three mechanisms: 1) Viscous Effects - Dissipation of acoustic energy due to fluid friction which results in thermodynamically irreversible propagation of sound. 2) Heat Conduction Effects - Heat transfer between high and low temperature regions in the wave which result in non-adiabatic propagation of the sound. 3) Inter Molecular Energy Interchanges - Molecular energy relaxation effects which result in a time lag between changes in translational kinetic energy and the energy associated with rotation and vibration of the molecules. The following table illustrates the attenuation coefficient of sound at standard pressure ( kpa) in units of db/100m. Temperature Relative Humidity Frequency (Hz) o C (%) As frequency increases, absorption tends to increase - As Relative Humidity increases, absorption tends to decrease - There is no direct relationship between absorption and temperature - The net result of atmospheric absorption is to modify the sound propagation of a point source from 6 db/doubling-of-distance to approximately 7 8 db/doubling-of-distance (based on anecdotal experience) 32

33 Sound Pressure Level (db) khz Base 1 khz 500 Hz 250 Hz 125 Hz 4 khz 20 8 khz distance (m) Atmospheric Absorption at 10 o C and 70% RH 33

34 Meteorological Effects There are many meteorological factors which can affect how sound propagates over large distances. These various phenomena must be considered when trying to determine the relative impact of a noise source either after installation or during the design stage. Wind - Can greatly alter the noise climate away from a source depending on direction - Sound levels downwind from a source can be increased due to refraction of sound back down towards the surface. This is due to the generally higher velocities as altitude increases. - Sound levels upwind from a source can be decreased due to a bending of the sound away from the earth s surface. - Sound level differences of ±10dB are possible depending on severity of wind and distance from source. - Sound levels crosswind are generally not disturbed by an appreciable amount - Wind tends to generate its own noise, however, and can provide a high degree of masking relative to a noise source of particular interest. Temperature - Temperature effects can be similar to wind effects - Typically, the temperature is warmer at ground level than it is at higher elevations. - If there is a very large difference between the ground temperature (very warm) and the air aloft (only a few hundred meters) then the transmitted sound refracts upward due to the changing speed of sound. - If the air aloft is warmer than the ground temperature (known as an inversion) the resulting higher speed of sound aloft tends to refract the transmitted sound back down towards the ground. This essentially works on Snell s law of reflection and refraction. - Temperature inversions typically happen early in the morning and are most common over large bodies of water or across river valleys. - Sound level differences of ±10dB are possible depending on gradient of temperature and distance from source. Rain - Rain does not affect sound propagation by an appreciable amount unless it is very heavy - The larger concern is the noise generated by the rain itself. A heavy rain striking the ground can cause a significant amount of highly broadband noise. The amount of noise generated is difficult to predict. - Rain can also affect the output of various noise sources such as vehicle traffic. Summary - In general, these wind and temperature effects are difficult to predict - Empirical models (based on measured data) have been generated to attempt to account for these effects. - Environmental noise measurements must be conducted with these effects in mind. Sometimes it is desired to have completely calm conditions, other times a worst case of downwind noise levels are desired. 34

35 Topographical Effects Similar to the various atmospheric effects outlined in the previous section, the effect of various geographical and vegetative factors must also be considered when examining the propagation of noise over large distances. Topography - One of the most important factors in sound propagation. - Can provide a natural barrier between source and receiver (i.e. if berm or hill in between). - Can provide a natural amplifier between source and receiver (i.e. large valley in between or hard reflective surface in between). - Must look at location of topographical features relative to source and receiver to determine importance (i.e. small berm 1km away from source and 1km away from receiver will make negligible impact). Grass - Can be an effective absorber due to large area covered - Only effective at low height above ground. Does not affect sound transmitted direct from source to receiver if there is line of sight. - Typically less absorption than atmospheric absorption when there is line of sight. - Approximate rule of thumb based on empirical data is: = 18log10( f ) 31 ( db /100m) A g Where: Ag is the absorption amount Trees - Provide absorption due to foliage - Deciduous trees are essentially ineffective in the winter - Absorption depends heavily on density and height of trees - No data found on absorption of various kinds of trees - Large spans of trees are required to obtain even minor amounts of sound reduction - In many cases, trees can provide an effective visual barrier, even if the noise attenuation is negligible. Tree/Foliage attenuation from ISO :

36 Bodies of Water - Large bodies of water can provide the opposite effect to grass and trees. - Reflections caused by small incidence angles (grazing) can result in larger sound levels at great distances (increased reflectivity, Q). - Typically air temperatures are warmer high aloft since air temperatures near water surface tend to be more constant. Result is a high probability of temperature inversion. - Sound levels can carry much further. Snow - Covers the ground for approximately 1/2 of the year in northern climates. - Can act as an absorber or reflector (and varying degrees in between). - Freshly fallen snow can be quite absorptive. - Snow which has been sitting for a while and hard packed due to wind can be quite reflective. - Falling snow can be more absorptive than rain, but does not tend to produce its own noise. - Snow can cover grass which might have provided some means of absorption. - Typically sound propagates with less impedance in winter due to hard snow on ground and no foliage on trees/shrubs. 36

37 Appendix III SOUND LEVELS OF FAMILIAR NOISE SOURCES Used with Permission Obtained from the Alberta Energy Regulator Directive 038 (February, 2007) Source 5 Sound Level ( dba) Bedroom of a country home Soft whisper at 1.5 m Quiet office or living room Moderate rainfall Inside average urban home Quiet street Normal conversation at 1 m Noisy office Noisy restaurant Highway traffic at 15 m Loud singing at 1 m Tractor at 15 m Busy traffic intersection Electric typewriter Bus or heavy truck at 15 m Jackhammer Loud shout Freight train at 15 m Modified motorcycle Jet taking off at 600 m Amplified rock music Jet taking off at 60 m Air-raid siren Cottrell, Tom, 1980, Noise in Alberta, Table 1, p.8, ECA80-16/1B4 (Edmonton: Environment Council of Alberta). 37

38 SOUND LEVELS GENERATED BY COMMON APPLIANCES Used with Permission Obtained from the Alberta Energy Regulator Directive 038 (February, 2007) Source 6 Sound level at 3 feet (dba) Freezer Refrigerator Electric heater Hair clipper Electric toothbrush Humidifier Clothes dryer Air conditioner Electric shaver Water faucet Hair dryer Clothes washer Dishwasher Electric can opener Food mixer Electric knife Electric knife sharpener Sewing machine Vacuum cleaner Food blender Coffee mill Food waste disposer Edger and trimmer Home shop tools Hedge clippers Electric lawn mower Reif, Z. F., and Vermeulen, P. J., 1979, Noise from domestic appliances, construction, and industry, Table 1, p.166, in Jones, H. W., ed., Noise in the Human Environment, vol. 2, ECA79-SP/1 (Edmonton: Environment Council of Alberta). 38

39 Appendix IV USBM RI-8507 CRITERIA 60 USBM Criteria mm/s Hz 1.00Hz 1.25Hz 1.60Hz 2.00Hz 2.50Hz 3.15Hz 4.00Hz 5.00Hz 6.30Hz 8.00Hz 10.0Hz 12.5Hz 16.0Hz 20.0Hz 25.0Hz 31.5Hz 40.0Hz 50.0Hz 63.0Hz 80.0Hz 100.0Hz 125.0Hz 160.0Hz 200.0Hz 39

40 Appendix V TABLE 1 FROM ISO 4866:1990(e) Frequency Amplitude Particle Velocity Particle Acceleration Time Measuring Vibration Forcing Function Range Range Range Range Characteristic Quantities (Hz) (µm) (mm/s) (m/s 2 ) Traffic Road, Rail, Ground-borne 1 to 80 1 to to to 1 C/T pvth Blasting Vibration Ground-borne 1 to to to to 50 T pvth Pile-Driving Ground-borne 1 to to to to 2 T pvth Machinery Outside Ground-borne 1 to to to to 1 C/T pvth/ath Acoustic Traffic, Machinery Outside 10 to to to to 1 C pvth/ath Air over Pressure 1 to 40 T pvth Machinery Inside 1 to to to to 1 C/T pvth/ath Human Activities a) Impact 0.1 to to to to 50 T pvth/ath b) direct 0.1 to to to to 0.2 T pvth/ath Earthquakes 0.1 to to to to 20 T pvth/ath Wind 0.1 to to T ath Acoustic Inside 5 to 500 Key: C = Continuous T = Transient pvth = Particle Velocity Time History ath = Acceleration Time History 40