Journal of the Acoustical Society of America, Oct 1, 2017
This paper estimates seabed and water-column properties of a shallow-water site in the Chukchi Se... more This paper estimates seabed and water-column properties of a shallow-water site in the Chukchi Sea using vessel noise recorded on a single ocean-bottom hydrophone. A shallow-hazards seismic survey vessel transited with a fixed heading, passing within 200 m of the hydrophone. Sound pressure levels as a function of frequency and range are inverted using a trans-dimensional (trans-D) Bayesian approach to estimate range-independent environmental properties (sound-speed profile, water depth, and seabed geoacoustic properties). The trans-D inversion allows the data to determine the most appropriate environmental model parameterization in terms of the number of sound-speed profile nodes and subbottom layers. The inversion also estimates the vessel source levels, source depth, hydrophone height above the seabed, a range-correction factor, and error statistics, and provides uncertainty estimates for all model parameters and parameterizations. The sound-speed profile is found to be in good agreement with a measured profile, and the upper sediment-layer sound speed agrees with estimates from separate inversions of airgun and bowhead whale modal dispersion data. This method could be applied to monitor sound-speed profile changes over long time scales, e.g., using Automatic Identification System position data for vessels in a shipping lane.
Journal of the Acoustical Society of America, May 1, 2017
This paper estimates seabed and water-column properties of a shallow-water site in the Chukchi Se... more This paper estimates seabed and water-column properties of a shallow-water site in the Chukchi Sea using bowhead whale calls recorded on asynchronous ocean-bottom hydrophones. Up- and down-swept bowhead whale calls were recorded on a cluster of seven hydrophones within a 5 km radius. The calls excited multiple propagating modes, with modal dispersion controlled by environmental properties and whale-recorder range. Frequency-dependent mode arrival times for nine whale calls are inverted using a trans-dimensional (trans-D) Bayesian approach that estimates the whale locations (easting and northing) and range-independent environmental properties (sound-speed profile, water depth, and seabed geoacoustic profiles). The trans-D inversion allows the data to determine the most appropriate environmental model parameterization in terms of the number of sound-speed profile nodes and subbottom layers. The inversion also estimates each whale-call instantaneous frequency function, relative recorder clock offsets, and residual-error standard deviation, and provides uncertainty estimates for all model parameters and parameterizations. The sound-speed profile is found to be poorly resolved, but water depth and upper sediment-layer thickness and sound speed are reasonably well resolved. Model estimates and uncertainties are compared to those from separate inversions involving airgun dispersion and vessel noise data collected nearby (which also represent sources of opportunity).
Journal of the Acoustical Society of America, Apr 1, 2016
It is a common practice for regulators to require project proponents to estimate the radius aroun... more It is a common practice for regulators to require project proponents to estimate the radius around a sound source where marine life could be injured or disturbed. Acoustic propagation modeling is normally required so that realistic radii are obtained that take into account the bathymetry, bottom properties, water column sound velocity profile, as well as source spectrum and directivity. Increasingly proponents are also asked to perform in-situ sound source characterization (SSC) measurements to verify the modeling predictions, including the spectrum and directivity of the sound source. During an SSC, sound levels are measured at increasing range from the source. In most cases, it is not possible to measure the sound levels at all ranges of interest, and therefore, the data must be interpolated or extrapolated to estimate the radii of the regulatory sound isopleths. This talk uses real-world data to identify the strengths and weaknesses of four methods of estimating the radii: (1) the practical spreading model; (2) linear interpolation; (3) linear regression with absorption; and (4) model-measured fits.
Journal of the Acoustical Society of America, Oct 1, 2004
Environmental impact assessments for seismic surveys often include estimates of radially propagat... more Environmental impact assessments for seismic surveys often include estimates of radially propagating sound levels, which are used to determine marine mammal impact zones. Sound levels may be estimated using computer-based acoustic modelling techniques but these require an accurate description of the survey source signature—arrays of airguns, in particular, have complex, highly directional source functions that depend on the array layout. To address this requirement, an airgun array source signature model has been developed for the purpose of underwater noise level prediction. The source model is based on published descriptions of the physics of airgun bubble oscillations and radiation [A. Ziolkowski, Geophys. J. R. Astron. Soc. 21, 137–161 (1970)] and includes the effects of port throttling, motion damping and bubble interactions. The output of the model is a collection of notional signatures which may be used to compute the source function of the array in any direction. Free parameters in the model have been fit to a large collection of existing airgun signature data, for airguns ranging from 5 to 185 in3. The output of the model is suitable for estimating sound levels resulting from airgun survey activity. [Work supported by NSERC.]
Journal of the Acoustical Society of America, Oct 1, 2019
Measurements from the large ship noise database acquired by the Vancouver Fraser Port Authority’s... more Measurements from the large ship noise database acquired by the Vancouver Fraser Port Authority’s Enhancing Cetacean Habitat Observation (ECHO) program were used to assess the conservativeness of five vessel noise certification societies. A multi-variate linear regression analysis of the database was used to scale ECHO measurements to a common reference vessel type for each of 6 categories: tug, tanker, bulker, container ship, vehicle carrier, cruise ship. The purpose of scaling the ECHO measurements was to create a modified dataset to compare with existing vessel noise certification society noise thresholds. The conservativeness of the certification society thresholds was found to vary with vessel category. The general findings are that the society limits are conservative for faster categories (e.g., container ship) but not for slower vessels such as tankers, and certification systems using monopole source level (MSL) had better matches with measurement data than the approaches using radiated noise level (RNL). None of the certification societies accounts for differences of vessels within a vessel category. Therefore, small ships are currently evaluated against the same threshold criteria as large ships. The scaling system developed here using the ECHO dataset could be used to scale measurements (or thresholds) to account for different vessel sizes and operating conditions. This research was funded by Transport Canada.
Journal of the Acoustical Society of America, Oct 1, 2019
The Vancouver Fraser Port Authority’s Enhancing Cetacean Habitat Observation (ECHO) program acqui... more The Vancouver Fraser Port Authority’s Enhancing Cetacean Habitat Observation (ECHO) program acquired a large database of several thousand systematic commercial ship noise measurements between September 2015 and April 2017. These measurements were used to develop a multi-variate linear regression model of vessel source levels against several parameters that describe vessels and their measurement conditions. Covariates in the multi-variate model included ship category, ship length, dead-weight-tonnage, static draught, effective wind speed magnitude and direction, ship speed, and surface angle. The regression analysis examined the statistical significance of each covariate’s regression coefficient and produced a set of fit coefficients, one for each covariate for each frequency band. The multi-variate model was used to normalize the measurements for each category, and the remaining data variance reflected vessel-specific differences in noise emissions that could not be attributed to measurement circumstances. The multivariate analysis produced a powerful ship noise model that can predict decidecade band monopole source level (MSL) and radiated noise level (RNL), which is useful for understanding noise emissions variations with ship characteristics and under different operating conditions. [This research was funded by Transport Canada.]
Journal of the Acoustical Society of America, Apr 1, 2016
This paper estimates bowhead whale locations and uncertainties using linearized Bayesian inversio... more This paper estimates bowhead whale locations and uncertainties using linearized Bayesian inversion of the time-difference-of-arrival (TDOA) of whale calls recorded on omni-directional asynchronous recorders in the Chukchi Sea, Alaska. A Y-shaped cluster of seven autonomous ocean-bottom hydrophones, separated by 0.5–9.2 km, was deployed for several months over which time their clocks drifted out of synchronization. Hundreds of recorded whale calls are manually annotated with time-frequency bounds and associated between recorders. The TDOA between all hydrophone pairs are calculated from filtered waveform cross-correlations and depend on the whale locations, hydrophone locations, relative recorder clock drifts, and an effective waveguide sound speed. The inversion estimates all of these parameters and their uncertainties as well as data error statistics using prior information to constrain the otherwise underdetermined problem. Whale location uncertainties are estimated to be approximately 100 m which allows tracking whales that vocalize repeatedly over several minutes. Estimates of clock drift rates are obtained from inversions of TDOA data over several weeks. The inversion is computationally efficient and suitable for application to large datasets of manually- or automatically detected whale calls.
Journal of the Acoustical Society of America, Apr 1, 2016
This paper estimates bowhead whale locations and environmental properties using Bayesian inversio... more This paper estimates bowhead whale locations and environmental properties using Bayesian inversion of the modal dispersion of whale calls recorded on asynchronous recorders in the shallow waters of the northeastern Chukchi Sea, Alaska. Bowhead calls were recorded on a Y-shaped cluster of seven autonomous ocean-bottom hydrophones, separated by up to 9.2 km. We use a warping time-frequency analysis to obtain frequency-dependent relative mode arrival times for nine frequency-modulated whale calls. Trans-dimensional inversion is applied to invert mode arrival times for the whale location, water sound-speed profile, subbottom layering and geoacoustic parameters, source instantaneous frequency (IF), relative recorder clock drifts, and residual error standard deviation, all with estimated uncertainties. Joint inversion of multiple calls is found to substantially reduce uncertainties on whale location, source IF, and clock drifts. Estimated whale location uncertainties are 30–160 m and clock drift uncertainties are 3–26 ms. The prior and posterior probability densities for environmental parameters are used to quantify transmission loss uncertainties corresponding to different levels of environmental knowledge, with applications to computing marine-mammal sound exposure levels.
A collaborative project between Port Metro Vancouver, Transport Canada, Ocean Networks Canada (ON... more A collaborative project between Port Metro Vancouver, Transport Canada, Ocean Networks Canada (ONC) and JASCO Applied Sciences (Canada) Ltd., has installed an underwater listening station along the northbound (incoming) shipping route to Burrard Inlet. This system is designed to characterize the acoustic emissions of large numbers of vessels that transit a predefined source measurement track. The results are important for assessing marine fauna exposures to noise throughout the Salish Sea and for designing possible vessel noise mitigation strategies. The underwater listening station consists of two AMAR Observer systems from JASCO Applied Sciences, connected to ONC’s VENUS East Node underwater observatory. Each AMAR Observer can accurately track vessels and simultaneously measure vessel sound levels using tetrahedral hydrophone arrays. Further vessel tracking information is provided by a dedicated vessel Automatic Identification System (AIS) installed by ONC. Acoustic data are digitized at 64 kHz on all 8 hydrophone channels, producing a large amount of data (1.5 MB per second). ONC’s East Node also collects salinity, temperature, and water current data. All acoustic and oceanographic data are transmitted in real-time over the VENUS network to ONC’s shore-based storage and high-performance-computer processing systems at University of Victoria. There, JASCO’s automated acoustic software analyzes the data and produces source level measurement reports for each vessel pass. The acoustic range has additional capabilities, including the automatic detection of marine mammal calls and measurement of ambient noise levels. In this presentation we will outline the technical design of the underwater listening station and we will discuss the purpose of these measurements and their relevance for assessing vessel noise in the Salish Sea
Journal of the Acoustical Society of America, Oct 1, 2017
This paper estimates seabed and water-column properties of a shallow-water site in the Chukchi Se... more This paper estimates seabed and water-column properties of a shallow-water site in the Chukchi Sea using vessel noise recorded on a single ocean-bottom hydrophone. A shallow-hazards seismic survey vessel transited with a fixed heading, passing within 200 m of the hydrophone. Sound pressure levels as a function of frequency and range are inverted using a trans-dimensional (trans-D) Bayesian approach to estimate range-independent environmental properties (sound-speed profile, water depth, and seabed geoacoustic properties). The trans-D inversion allows the data to determine the most appropriate environmental model parameterization in terms of the number of sound-speed profile nodes and subbottom layers. The inversion also estimates the vessel source levels, source depth, hydrophone height above the seabed, a range-correction factor, and error statistics, and provides uncertainty estimates for all model parameters and parameterizations. The sound-speed profile is found to be in good agreement with a measured profile, and the upper sediment-layer sound speed agrees with estimates from separate inversions of airgun and bowhead whale modal dispersion data. This method could be applied to monitor sound-speed profile changes over long time scales, e.g., using Automatic Identification System position data for vessels in a shipping lane.
Journal of the Acoustical Society of America, May 1, 2017
This paper estimates seabed and water-column properties of a shallow-water site in the Chukchi Se... more This paper estimates seabed and water-column properties of a shallow-water site in the Chukchi Sea using bowhead whale calls recorded on asynchronous ocean-bottom hydrophones. Up- and down-swept bowhead whale calls were recorded on a cluster of seven hydrophones within a 5 km radius. The calls excited multiple propagating modes, with modal dispersion controlled by environmental properties and whale-recorder range. Frequency-dependent mode arrival times for nine whale calls are inverted using a trans-dimensional (trans-D) Bayesian approach that estimates the whale locations (easting and northing) and range-independent environmental properties (sound-speed profile, water depth, and seabed geoacoustic profiles). The trans-D inversion allows the data to determine the most appropriate environmental model parameterization in terms of the number of sound-speed profile nodes and subbottom layers. The inversion also estimates each whale-call instantaneous frequency function, relative recorder clock offsets, and residual-error standard deviation, and provides uncertainty estimates for all model parameters and parameterizations. The sound-speed profile is found to be poorly resolved, but water depth and upper sediment-layer thickness and sound speed are reasonably well resolved. Model estimates and uncertainties are compared to those from separate inversions involving airgun dispersion and vessel noise data collected nearby (which also represent sources of opportunity).
Journal of the Acoustical Society of America, Apr 1, 2016
It is a common practice for regulators to require project proponents to estimate the radius aroun... more It is a common practice for regulators to require project proponents to estimate the radius around a sound source where marine life could be injured or disturbed. Acoustic propagation modeling is normally required so that realistic radii are obtained that take into account the bathymetry, bottom properties, water column sound velocity profile, as well as source spectrum and directivity. Increasingly proponents are also asked to perform in-situ sound source characterization (SSC) measurements to verify the modeling predictions, including the spectrum and directivity of the sound source. During an SSC, sound levels are measured at increasing range from the source. In most cases, it is not possible to measure the sound levels at all ranges of interest, and therefore, the data must be interpolated or extrapolated to estimate the radii of the regulatory sound isopleths. This talk uses real-world data to identify the strengths and weaknesses of four methods of estimating the radii: (1) the practical spreading model; (2) linear interpolation; (3) linear regression with absorption; and (4) model-measured fits.
Journal of the Acoustical Society of America, Oct 1, 2004
Environmental impact assessments for seismic surveys often include estimates of radially propagat... more Environmental impact assessments for seismic surveys often include estimates of radially propagating sound levels, which are used to determine marine mammal impact zones. Sound levels may be estimated using computer-based acoustic modelling techniques but these require an accurate description of the survey source signature—arrays of airguns, in particular, have complex, highly directional source functions that depend on the array layout. To address this requirement, an airgun array source signature model has been developed for the purpose of underwater noise level prediction. The source model is based on published descriptions of the physics of airgun bubble oscillations and radiation [A. Ziolkowski, Geophys. J. R. Astron. Soc. 21, 137–161 (1970)] and includes the effects of port throttling, motion damping and bubble interactions. The output of the model is a collection of notional signatures which may be used to compute the source function of the array in any direction. Free parameters in the model have been fit to a large collection of existing airgun signature data, for airguns ranging from 5 to 185 in3. The output of the model is suitable for estimating sound levels resulting from airgun survey activity. [Work supported by NSERC.]
Journal of the Acoustical Society of America, Oct 1, 2019
Measurements from the large ship noise database acquired by the Vancouver Fraser Port Authority’s... more Measurements from the large ship noise database acquired by the Vancouver Fraser Port Authority’s Enhancing Cetacean Habitat Observation (ECHO) program were used to assess the conservativeness of five vessel noise certification societies. A multi-variate linear regression analysis of the database was used to scale ECHO measurements to a common reference vessel type for each of 6 categories: tug, tanker, bulker, container ship, vehicle carrier, cruise ship. The purpose of scaling the ECHO measurements was to create a modified dataset to compare with existing vessel noise certification society noise thresholds. The conservativeness of the certification society thresholds was found to vary with vessel category. The general findings are that the society limits are conservative for faster categories (e.g., container ship) but not for slower vessels such as tankers, and certification systems using monopole source level (MSL) had better matches with measurement data than the approaches using radiated noise level (RNL). None of the certification societies accounts for differences of vessels within a vessel category. Therefore, small ships are currently evaluated against the same threshold criteria as large ships. The scaling system developed here using the ECHO dataset could be used to scale measurements (or thresholds) to account for different vessel sizes and operating conditions. This research was funded by Transport Canada.
Journal of the Acoustical Society of America, Oct 1, 2019
The Vancouver Fraser Port Authority’s Enhancing Cetacean Habitat Observation (ECHO) program acqui... more The Vancouver Fraser Port Authority’s Enhancing Cetacean Habitat Observation (ECHO) program acquired a large database of several thousand systematic commercial ship noise measurements between September 2015 and April 2017. These measurements were used to develop a multi-variate linear regression model of vessel source levels against several parameters that describe vessels and their measurement conditions. Covariates in the multi-variate model included ship category, ship length, dead-weight-tonnage, static draught, effective wind speed magnitude and direction, ship speed, and surface angle. The regression analysis examined the statistical significance of each covariate’s regression coefficient and produced a set of fit coefficients, one for each covariate for each frequency band. The multi-variate model was used to normalize the measurements for each category, and the remaining data variance reflected vessel-specific differences in noise emissions that could not be attributed to measurement circumstances. The multivariate analysis produced a powerful ship noise model that can predict decidecade band monopole source level (MSL) and radiated noise level (RNL), which is useful for understanding noise emissions variations with ship characteristics and under different operating conditions. [This research was funded by Transport Canada.]
Journal of the Acoustical Society of America, Apr 1, 2016
This paper estimates bowhead whale locations and uncertainties using linearized Bayesian inversio... more This paper estimates bowhead whale locations and uncertainties using linearized Bayesian inversion of the time-difference-of-arrival (TDOA) of whale calls recorded on omni-directional asynchronous recorders in the Chukchi Sea, Alaska. A Y-shaped cluster of seven autonomous ocean-bottom hydrophones, separated by 0.5–9.2 km, was deployed for several months over which time their clocks drifted out of synchronization. Hundreds of recorded whale calls are manually annotated with time-frequency bounds and associated between recorders. The TDOA between all hydrophone pairs are calculated from filtered waveform cross-correlations and depend on the whale locations, hydrophone locations, relative recorder clock drifts, and an effective waveguide sound speed. The inversion estimates all of these parameters and their uncertainties as well as data error statistics using prior information to constrain the otherwise underdetermined problem. Whale location uncertainties are estimated to be approximately 100 m which allows tracking whales that vocalize repeatedly over several minutes. Estimates of clock drift rates are obtained from inversions of TDOA data over several weeks. The inversion is computationally efficient and suitable for application to large datasets of manually- or automatically detected whale calls.
Journal of the Acoustical Society of America, Apr 1, 2016
This paper estimates bowhead whale locations and environmental properties using Bayesian inversio... more This paper estimates bowhead whale locations and environmental properties using Bayesian inversion of the modal dispersion of whale calls recorded on asynchronous recorders in the shallow waters of the northeastern Chukchi Sea, Alaska. Bowhead calls were recorded on a Y-shaped cluster of seven autonomous ocean-bottom hydrophones, separated by up to 9.2 km. We use a warping time-frequency analysis to obtain frequency-dependent relative mode arrival times for nine frequency-modulated whale calls. Trans-dimensional inversion is applied to invert mode arrival times for the whale location, water sound-speed profile, subbottom layering and geoacoustic parameters, source instantaneous frequency (IF), relative recorder clock drifts, and residual error standard deviation, all with estimated uncertainties. Joint inversion of multiple calls is found to substantially reduce uncertainties on whale location, source IF, and clock drifts. Estimated whale location uncertainties are 30–160 m and clock drift uncertainties are 3–26 ms. The prior and posterior probability densities for environmental parameters are used to quantify transmission loss uncertainties corresponding to different levels of environmental knowledge, with applications to computing marine-mammal sound exposure levels.
A collaborative project between Port Metro Vancouver, Transport Canada, Ocean Networks Canada (ON... more A collaborative project between Port Metro Vancouver, Transport Canada, Ocean Networks Canada (ONC) and JASCO Applied Sciences (Canada) Ltd., has installed an underwater listening station along the northbound (incoming) shipping route to Burrard Inlet. This system is designed to characterize the acoustic emissions of large numbers of vessels that transit a predefined source measurement track. The results are important for assessing marine fauna exposures to noise throughout the Salish Sea and for designing possible vessel noise mitigation strategies. The underwater listening station consists of two AMAR Observer systems from JASCO Applied Sciences, connected to ONC’s VENUS East Node underwater observatory. Each AMAR Observer can accurately track vessels and simultaneously measure vessel sound levels using tetrahedral hydrophone arrays. Further vessel tracking information is provided by a dedicated vessel Automatic Identification System (AIS) installed by ONC. Acoustic data are digitized at 64 kHz on all 8 hydrophone channels, producing a large amount of data (1.5 MB per second). ONC’s East Node also collects salinity, temperature, and water current data. All acoustic and oceanographic data are transmitted in real-time over the VENUS network to ONC’s shore-based storage and high-performance-computer processing systems at University of Victoria. There, JASCO’s automated acoustic software analyzes the data and produces source level measurement reports for each vessel pass. The acoustic range has additional capabilities, including the automatic detection of marine mammal calls and measurement of ambient noise levels. In this presentation we will outline the technical design of the underwater listening station and we will discuss the purpose of these measurements and their relevance for assessing vessel noise in the Salish Sea
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