Range dependent nature of impulsive noise Final Report

Matei, M.; Chudzinska, M.; Remmers, P.; Bellmann, M.; Darias-O’Hara, A.; Verfuss, U.; Wood, J.; Hardy, N.; Wilder, F.; Booth, C. (2024). Range dependent nature of impulsive noise Final Report. Report by SMRU Consulting. Report for Offshore Renewables Joint Industry Programme (ORJIP).

@techreport{Matei-2024-2131022,
author = {Matei, M and Chudzinska, M and Remmers, P and Bellmann, M and Darias-O’Hara, A and Verfuss, U and Wood, J and Hardy, N and Wilder, F and Booth, C},
title = {Range dependent nature of impulsive noise Final Report},
institution = {SMRU Consulting},
year = {2024},
month = {may},
address = {Scotland, United Kingdom},
url = {https://www.carbontrust.com/our-work-and-impact/guides-reports-and-tools/orjip-range-dependent-nature-of-impulsive-noise-radin},
keywords = {Wind Energy, Fixed Offshore Wind, Noise, Marine Mammals},
}

Export Citation to BibTex

TY - RPRT
TI - Range dependent nature of impulsive noise Final Report
AU - Matei, M
AU - Chudzinska, M
AU - Remmers, P
AU - Bellmann, M
AU - Darias-O’Hara, A
AU - Verfuss, U
AU - Wood, J
AU - Hardy, N
AU - Wilder, F
AU - Booth, C
AB - Multiple studies across various animal taxa have concluded that, at comparable sound levels, impulsive noise is generally more hazardous for animal hearing than non-impulsive noise. However, as impulsive noise travels further away from the source, its energy is manipulated and it is absorbed by the environment. This energy dissipation and the way signals travel and get reflected off the seabed and sea surface lead to a loss of impulsive characteristics as a function of distance from the sound source.The objective of this study was to improve our understanding of how the impulsiveness of sounds produced during pile driving and unexploded ordnance clearances changes with increasing distance from the source, and to help refine the estimation of auditory injury impact ranges for marine mammals during noise impact assessments.A literature review was conducted to identify metrics that characterise signal impulsiveness. The identified metrics were then extracted from field acoustic recordings collected during unabated impact pile driving activities and unexploded ordnance clearance. The resulting dataset for impact pile driving activities was supplemented by metadata which included pile characteristics (pile type and diameter), hammer energy, environmental variables (bathymetry and sediment type), as well as spatial and temporal attributes (distance from the pile and time since the first pile strike, respectively). The dataset for unexploded ordnance was accompanied by metadata concerning the placement of the acoustic recorders and charge weight.Four metrics of impulsiveness collected from the pile driving dataset (kurtosis, crest factor, peak sound pressure level, and high frequency content) were modelled to investigate changes with range and other variables and to assess at what distance impulsive sounds transition to being non-impulsive, based on thresholds from the scientific literature. This study has shown a decrease in impulsiveness as sounds travel further away from the source. Although a marked decrease was noted in all metrics of impulsiveness within the first five kilometres from the piling location, there is still insufficient evidence to establish a range of distances from which these sounds are no longer impulsive. This is driven by limitations in the available data on auditory impacts from signals with intermediary levels of impulsiveness.In parallel to the assessment of field data, a framework (software tool) was developed for estimating permanent hearing damage impact ranges from impact pile driving by considering a variety of factors. The framework allows the user flexibility to test different scenarios by varying: how the soundscape is modelled (by changing the source level and transmission loss, as well as the time interval between pile strikes), how animals react to piling (by changing the fleeing speed), and the assumed distance threshold at which sound becomes non-impulsive. Simulations involving standardised fleeing speed, transmission loss and source level indicated that when the transition from impulsiveness to non- impulsiveness occurred at 5 km from the piling source, the permanent hearing damage impact ranges were equal to those from instances where this transition occurred at 50 km. Scenarios where this transition occurred at ranges less than 5 km from the piling source resulted in reduced impact ranges.Additionally, simulated scenarios using piling sequences from 44 representative hammer logs (out of over 200 provided from offshore wind developments) suggest that the assumptions assessed in noise impact assessments may result in an overestimation of the auditory injury impact ranges (a median percentage reduction in PTS impact area of 57%). The time between subsequent pile strikes in the first 45 minutes of piling was found to have the largest effect on hearing damage onset ranges (for a standardised source level, transmission loss, and animal swim speed) compared to characteristics like the total duration of piling. The simulations involving real hammer logs with longer periods between subsequent pile strikes in the first 45 minutes of piling produced smaller impact ranges. The framework developed here could be used to help design installation blow temporal patterns to help minimise impacts at the design or pre-consent stage.
CY - Scotland, United Kingdom
DA - 2024/05//
PY - 2024
SP - 1
EP - 130
PB - SMRU Consulting
UR - https://www.carbontrust.com/our-work-and-impact/guides-reports-and-tools/orjip-range-dependent-nature-of-impulsive-noise-radin
LA - English
KW - Wind Energy
KW - Fixed Offshore Wind
KW - Noise
KW - Marine Mammals
ER -

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Abstract

Multiple studies across various animal taxa have concluded that, at comparable sound levels, impulsive noise is generally more hazardous for animal hearing than non-impulsive noise. However, as impulsive noise travels further away from the source, its energy is manipulated and it is absorbed by the environment. This energy dissipation and the way signals travel and get reflected off the seabed and sea surface lead to a loss of impulsive characteristics as a function of distance from the sound source.

The objective of this study was to improve our understanding of how the impulsiveness of sounds produced during pile driving and unexploded ordnance clearances changes with increasing distance from the source, and to help refine the estimation of auditory injury impact ranges for marine mammals during noise impact assessments.

A literature review was conducted to identify metrics that characterise signal impulsiveness. The identified metrics were then extracted from field acoustic recordings collected during unabated impact pile driving activities and unexploded ordnance clearance. The resulting dataset for impact pile driving activities was supplemented by metadata which included pile characteristics (pile type and diameter), hammer energy, environmental variables (bathymetry and sediment type), as well as spatial and temporal attributes (distance from the pile and time since the first pile strike, respectively). The dataset for unexploded ordnance was accompanied by metadata concerning the placement of the acoustic recorders and charge weight.

Four metrics of impulsiveness collected from the pile driving dataset (kurtosis, crest factor, peak sound pressure level, and high frequency content) were modelled to investigate changes with range and other variables and to assess at what distance impulsive sounds transition to being non-impulsive, based on thresholds from the scientific literature. This study has shown a decrease in impulsiveness as sounds travel further away from the source. Although a marked decrease was noted in all metrics of impulsiveness within the first five kilometres from the piling location, there is still insufficient evidence to establish a range of distances from which these sounds are no longer impulsive. This is driven by limitations in the available data on auditory impacts from signals with intermediary levels of impulsiveness.

In parallel to the assessment of field data, a framework (software tool) was developed for estimating permanent hearing damage impact ranges from impact pile driving by considering a variety of factors. The framework allows the user flexibility to test different scenarios by varying: how the soundscape is modelled (by changing the source level and transmission loss, as well as the time interval between pile strikes), how animals react to piling (by changing the fleeing speed), and the assumed distance threshold at which sound becomes non-impulsive. Simulations involving standardised fleeing speed, transmission loss and source level indicated that when the transition from impulsiveness to non- impulsiveness occurred at 5 km from the piling source, the permanent hearing damage impact ranges were equal to those from instances where this transition occurred at 50 km. Scenarios where this transition occurred at ranges less than 5 km from the piling source resulted in reduced impact ranges.

Additionally, simulated scenarios using piling sequences from 44 representative hammer logs (out of over 200 provided from offshore wind developments) suggest that the assumptions assessed in noise impact assessments may result in an overestimation of the auditory injury impact ranges (a median percentage reduction in PTS impact area of 57%). The time between subsequent pile strikes in the first 45 minutes of piling was found to have the largest effect on hearing damage onset ranges (for a standardised source level, transmission loss, and animal swim speed) compared to characteristics like the total duration of piling. The simulations involving real hammer logs with longer periods between subsequent pile strikes in the first 45 minutes of piling produced smaller impact ranges. The framework developed here could be used to help design installation blow temporal patterns to help minimise impacts at the design or pre-consent stage.