MECH9325_Lab1_z5312271

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1 Fundamentals of Acoustics and Noise MECH9325 Term 2, 2023 LAB 1 (Date of Submission: 27/06/2023)

i Table of Contents Task 1 ......................................................................................................................................... 1 Task 2 ......................................................................................................................................... 2 Task 3 ......................................................................................................................................... 5 References ................................................................................................................................. 6 Table of Figures Figure 1: Time history of the sound pressure level of the Pacific Highway recording, measured over a 3-minute period. .............................................................................................. 1 Figure 2: Time history of the sound pressure level of the anchor drilling site, measured over a 60 second period. ....................................................................................................................... 2 Figure 3: Time history of the sound pressure level of the hydraulic rock breaker, measured over a 60 second period. ............................................................................................................ 3 Figure 4: Time history of the sound pressure level of the excavator, measured over a 60 second period. ............................................................................................................................ 3 Figure 5: Time history of the sound pressure level of the garbage trucks unloading, measured over a 60 second period. ............................................................................................................ 4 Table of Figures Equation 1: Equation used to find the equivalent A-weighted SPL over total time T ............... 2

1 Task 1 Figure 1: Time history of the sound pressure level of the Pacific Highway recording, measured over a 3-minute period. Using the iNVH application and the Pacific Highway recording, a time history of the sound pressure level (dB(A)) of the recording was produced over a sampling period of 3 minutes. Using an Excel spreadsheet, the values of L Aeq , L A10 , and L A90 were derived. For L Aeq , the time interval between each measurement taken was calculated and substituted into Equation 1 alongside its respective instantaneous sound pressure level to find the L Aeq of the entire sample, which was found to be 69.29 dB(A). The values of L A10 and L A90 were calculated using the Excel functions PERCENTILE (array, 0.9) and PERCENTILE (array, 0.1), and were found to be 74.39 dB(A) and 54.12 dB(A) correspondingly. This data can be seen on Figure 1. L Aeq refers to the equivalent A-weighted sound pressure level over the entire period, as such, all sound affects the value of L Aeq as it seeks to describe what is the average noise level over a period [1]. L A10 refers to instances where the sound pressure level measured was equal to or exceeded for 10% of the measurement period [1]. This refers to instances of louder noise, such as the appearance of a heavy vehicle, a small vehicle close to the audio capturing device, or of an abundance of traffic passing by. Likewise, L A90 represents periods where the sound pressure level was equal to or exceeded for 90% of the time. Hence, L A90 describes the ambient noise and therefore, details the sound pressure level of the background noise of the recording, including things like the beeping of the pedestrian crossing signal, wind, etc. 0 10 20 30 40 50 60 70 80 90 0 5.201268 10.402548 15.603842 20.805136 26.00643 31.207724 36.409016 41.61031 46.811604 52.012897 57.214191 62.415485 67.616776 72.818069 78.019363 83.220657 88.421951 93.623245 98.824539 104.025833 109.227127 114.428421 119.629715 124.831009 130.032303 135.233597 140.434891 145.636185 150.837479 156.038773 161.240067 166.44136 171.642654 176.843948 Sound Pressure Level (dB(A)) Time (seconds) Time History of Sound Pressure Level for the Pacific Highway Recording OverallLevel LAEQ LA10 LA90

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2 Equation 1: Equation used to find the equivalent A-weighted SPL over total time T Task 2 Figure 2: Time history of the sound pressure level of the anchor drilling site, measured over a 60 second period. 0 10 20 30 40 50 60 70 80 0 1.764716 3.529432 5.294148 7.058864 8.823584 10.588308 12.353033 14.117758 15.882483 17.647207 19.411932 21.176657 22.941381 24.706106 26.470831 28.235556 30.00028 31.765005 33.529728 35.294453 37.059177 38.823902 40.588627 42.353352 44.118076 45.882801 47.647526 49.412251 51.176975 52.9417 54.706425 56.471149 58.235874 60.000599 Sound Pressure Level (dB(A)) Time (seconds) Time History of Sound Pressure Level of the Anchor Drilling Site OverallLevel LA90 LAMIN LAMAX LAEQ

3 Figure 3: Time history of the sound pressure level of the hydraulic rock breaker, measured over a 60 second period. Figure 4: Time history of the sound pressure level of the excavator, measured over a 60 second period. 0 10 20 30 40 50 60 70 80 0 1.671836 3.343673 5.015509 6.687345 8.359182 10.031027 11.702871 13.374716 15.04656 16.718405 18.390249 20.062094 21.733938 23.405783 25.077627 26.749472 28.421316 30.093161 31.765005 33.436848 35.108692 36.780537 38.452381 40.124226 41.79607 43.467915 45.139759 46.811604 48.483448 50.155293 51.827137 53.498981 55.170826 56.84267 58.514515 Time History of Sound Pressure Level of the Hydraulic Rock Breaker OverallLevel LA90 LAMIN LAMAX LAEQ 0 10 20 30 40 50 60 70 80 0 1.764716 3.529432 5.294148 7.058864 8.823584 10.588308 12.353033 14.117758 15.882483 17.647207 19.411932 21.176657 22.941381 24.706106 26.470831 28.235556 30.00028 31.765005 33.529728 35.294453 37.059177 38.823902 40.588627 42.353352 44.118076 45.882801 47.647526 49.412251 51.176975 52.9417 54.706425 56.471149 58.235874 60.000599 Sound pressure level (dB(A)) Time (seconds) Time History of Sound Pressure Level of the Excavator OverallLevel LA90 LAMAX LAEQ

4 Figure 5: Time history of the sound pressure level of the garbage trucks unloading, measured over a 60 second period. Steady noise, impulsive noise, and intermittent noise are three categories of noise often used to describe the noise present on a construction site or where heavy machinery is being operated. Steady noise refers to situations wherein there is a constant noise that only fluctuates in a 3 dB(A) range, intermittent refers to noise that fluctuates greater than 5 dB(A), whereas impulsive refers to short, sudden ‘impulses’ of sound pressure level that last less than a second and are much louder than the background noise [2]. For the recording of the anchor drilling site, its sound type can be described as an impulsive sound due to the sudden manoeuvring of heavy machinery, air release, and metal falling on metal which is laid against a quieter background noise consisting of the running of different generators, pumps, boring, and idling machinery. This can be seen in Figure 2, where the sound pressure level often fluctuates greater than 5 dB(A) for less than a second. For the recording of the hydraulic rock breaker, the sound type can be characterised as an intermittent noise due to the repetitive hammering, which also results in a fluctuation of more than 5 dB(A) over the measured time. This is reflected in Figure 3, which clearly illustrates the fluctuations in sound as a result. Similarly, the recording of the excavator can also be classified as an intermittent sound. From Figure 4, although most of the graph describes a steady noise when the excavator is being used to dig, when the excavator is being 0 10 20 30 40 50 60 70 80 90 0 1.671836 3.343673 5.015509 6.687345 8.359182 10.031027 11.702871 13.374716 15.04656 16.718405 18.390249 20.062094 21.733938 23.405783 25.077627 26.749472 28.421316 30.093161 31.765005 33.436848 35.108692 36.780537 38.452381 40.124226 41.79607 43.467915 45.139759 46.811604 48.483448 50.155293 51.827137 53.498981 55.170826 56.84267 58.514515 Time History of Sound Pressure Level of Garbage Trucks Unloading OverallLevel LA10 LA90 LAMAX LAEQ

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5 manoeuvred an intermittent sound can be heard due to the beeping that it emits when reversing. Finally, the recording of the garbage trucks unloading can be categorised as a steady noise, as there is no noise fluctuation present in the recording that is above 3 dB(A). For the series of recordings, the noise descriptors that were chosen were comprised of L AMIN, L AMAX , L Aeq and L A90 . L AMIN and L AMAX refers to the minimum and maximum sound pressure level values that are collated over the length of a recording. The purpose of these noise descriptors is to describe the impact of any potential intermittent or impulsive noise on listeners. L Aeq refers to the average sound pressure level of an environment over time. This is a key descriptor as it incorporates all sound types and produces a mean sound pressure level which a person experiences to ensure that an individual is operating at a safe level of noise exposure. In addition, the L Aeq descriptor is used in Australia under the Australian standard AS1269.1-1998. L A90 alludes to the sound pressure level that is present for 90% of the measured period, this descriptor usually indicates the steady ambient sound pressure level. This descriptor can be used to certify that the background noise does not exceed a dangerous level throughout the length of the recording. Task 3 The recordings of the anchor drilling site, hydraulic rock breaker, excavator and of the garbage trucks unloading had an L Aeq of 61.28 dB(A), 62.79 dB(A), 60.69 dB(A), and 68.65 dB(A) respectively. When using L Aeq as a descriptor for different types of anthropogenic environmental noise, it considers all types of noise – steady, intermittent, and impulsive noise – and dispenses an average sound pressure level for the period measured. When there are short term sound events, such as those with an impulsive sound type, it can skew the L Aeq value and result in an inaccurate average sound pressure level. As a result, it is unsuitable for cases where the sound source of interest emits a constant noise and where the ambient noise has a degree of fluctuation [3].

6 References [1 ] Department of Transport and Main Roads, Queensland Government, “Transport Noise Management Code of Practice: Volume 2 – Construction Noise and Vibration,” 29 July 2016. [Online]. Available: https://environment.des.qld.gov.au/__data/assets/pdf_file/0027/88560/eis-tm-noise- measurement-manual.pdf. [Accessed 24 June 2023]. [2 ] Department of Transport and Main Roads, Queensland Government, “Noise Measurement Manual,” 10 March 2020. [Online]. Available: https://environment.des.qld.gov.au/__data/assets/pdf_file/0026/88703/pr-cp-noise- and-vibration.pdf. [Accessed 24 June 2023]. [3 ] NSW Environment Protection Authority, “Noise Guide for Local Government Part 2 Noise assessment,” January 2023. [Online]. Available: https://www.epa.nsw.gov.au/~/media/EPA/Corporate%20Site/resources/noise/130127 NGLGPart2.ashx. [Accessed 26 June 2023].