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Mark McDonald

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University of Pretoria

Primrose Shabangu

University of Pretoria

Леонид Решетов

University of Washington

University of California, San Diego

Texas A&M University

University of California, San Diego

Arthur Teranishi

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Papers by Mark McDonald

Waveguide Propagation Allows Range Estimates for North Pacific Right Whales in the Bering Sea

Canadian Acoustics Acoustique Canadienne, 2004

The shallow and uniform water depth of the eastern Bering Sea shelf results in an acoustic wavegu... more The shallow and uniform water depth of the eastern Bering Sea shelf results in an acoustic waveguide. Propagation within this waveguide produces waveform dispersion which is dependent upon range. We present a means for using dispersed waveforms to determine range to calling whales from a single autonomous acoustic recording instrument. The predominant North Pacific right whale (Eubalaena japonica) call is frequency upswept from about 90 Hz to around 160 Hz and lasts approximately 1 s. The regional bathymetry of the eastern Bering Sea middle shelf is relatively uniform and shallow (~ 70 meters deep). This geometry provides a plane-layered waveguide in which right whale upswept calls can be detected at ranges over 50 km and have multiple modal arrivals that become dispersed, displaying different propagation velocities for different frequencies. Dispersion characteristics of modal arrivals are dependent on the calling whale's depth, the receiver's depth, the water depth, the range from caller to receiver, and various environmental parameters including water and sediment density and sound velocity. A model of sound propagation for the eastern Bering Sea middle shelf is developed from right whale call dispersion recorded on sonobuoys and seafloor acoustic recording packages, using individual calls recorded at multiple instruments. After development of the model, waveform dispersion allows estimation of caller range based on single instrument recordings. Estimating range between instrument and calling whales provides a means to estimate minimum abundance for the endangered North Pacific right whale.

Ocean ambient sound south of Bermuda and Panama Canal traffic

The Journal of the Acoustical Society of America, May 1, 2016

Comparisons of current and historic ocean ambient noise levels are rare, especially in the North ... more Comparisons of current and historic ocean ambient noise levels are rare, especially in the North Atlantic. Recent (2013-2014) monthly patterns in ocean ambient sound south of Bermuda were compared to those recorded at the same location in 1966. Additionally, trends in ocean traffic, in particular, Panama Canal traffic, over this time were also investigated. One year of ocean ambient noise measurements were collected in 1966 using cabled, omnidirectional hydrophones at the U.S. Navy Tudor Hill Laboratory in Bermuda, and repeat measurements were collected at the same location from June 2013-May 2014 using a High-frequency Acoustic Recording Package. Average monthly pressure spectrum levels at 44 Hz increased 2.8 ± 0.8 dB from 1966 to 2013, indicating an average increase of 0.6 dB/decade. This low level of increase may be due to topographic shielding at this site, limiting it to only southern exposure, and the limit in the number of ship transits through the Panama Canal, which did not...

Beaked Whale Presence, Habitat, and Sound Production in the North Pacific

Acoustic and Visual Detection of Large Whales in the Eastern North Pacific Ocean

Two cruises were conducted in the eastern North Pacific Ocean to investigate the precision of lar... more Two cruises were conducted in the eastern North Pacific Ocean to investigate the precision of large whale call locations as determined by the National Oceanic and Atmospheric Administration (NOAA) and Pacific Marine Environmental Laboratory's (PMEL) implementation of a localization and tracking routine using data from the U.S. Navy's Sound Surveillance System (SOSUS). Attempts to confirm SOSUS-derived large whale call locations by comparisons to standard vessel-based visual survey data were largely unsuccessful due to spatial and temporal differences in sampling scale.

Blue and fin whales observed on a seafloor array in the Northeast Pacific

Calling blue and fin whales have been tracked using relative travel times and amplitudes from bot... more Calling blue and fin whales have been tracked using relative travel times and amplitudes from both direct and multipath arrivals to a seafloor array of seismometers. Calls of three fin whales swimming in the same general direction, but several kilometers apart, are believed to represent communication between the whales because of signature differences in call character, an alternating call pattern, and coordination of call and respiration times. Whale call tracks, call patterns, call character, and swimming speeds were examined during periods with and without the presence of noise. Noise sources included airguns, when the whales were subject to sound levels of up to 143 dB P-P (peak-to-peak) re: 1 pPa over the 10 to 60-Hz band, and transits of merchant ships, when the whales received continuous levels up to 106 dB rms re: I /•Pa over the 10 to 60-Hz band (115 dB P-P). Whale responses associated with these noises remain arguable. ¸ 1995 Acoustical Society of America. PACS numbers: 43.80.Jz, 43.80.Ka, 43.80.Nd INTRODUCTION Many baleen whales produce loud low-frequency underwater sounds a significant percentage of the time, providing a practical tool with which to study whale distribution and movements (Watkins and Wartzok, 1985; Nishimura and Conlon, 1994; Clark, 1994). Studies of whales have used arrays of acoustic sensors to determine swimming speed and direction as well as to monitor call interaction between whales (Patterson and Hamilton, 1964; Cummings etal., 1968; Watkins and Schevill, 1977; Cummings and Holliday, 1985). Temporal patterns in acoustic call sequences provide a measure of respiration times (Cummings et al., 1986) while call characteristics may separate stocks or groups within the species (Winn et al., 1981; Ford and Fisher, 1983). Further study of whale calls may allow them to be used to monitor behavioral changes associated with man-made noise sources.

Microearthquakes at intermediate spreading-rate ridges: The Cleft segment megaplume site on the Juan de Fuca Ridge

... Kappel, ES and WR Normark (1987). Morphometric variability within the Axial Zone of the south... more

Mysticete whale acoustic and visual census in the SO GLOBEC West Antarctic Peninsula region

The distribution and relative abundance of mysticete whales in the SO GLOBEC West Antarctic Penin... more The distribution and relative abundance of mysticete whales in the SO GLOBEC West Antarctic Peninsula (WAP) region was investigated using acoustic and visual census techniques. Calls of three species (blue, fin and minke whales), recorded by autonomous acoustic recording packages (ARPs) were tallied for the period from April 2001 to February 2002. Blue and minke whale calls were recorded year-round, with calls from blue whales occurring far more frequently than those from minkes. Fin whale calls were strongly seasonal, with a peak in April-May 2001 and an absence of calls from July 2001 through January 2002. Calls from humpback whales were recorded on the ARPs but have not yet been tallied. Visual observations were conducted during eight SO GLOBEC cruises using standard line transect survey protocols, with resultant data confirming humpback and minke whale presence in the study region in austral autumn and winter. There was only one (possible) blue whale sighting and a few fin whale...

Biogeographic characterisation of blue whale song worldwide: Using song to identify populations

Journal of Cetacean Research and Management

Blue whale songs provide a new means for characterizing blue whale population structure worldwide... more Blue whale songs provide a new means for characterizing blue whale population structure worldwide. These songs are divided into nine regional types, which maintain a stable character. Five of the nine song types have been recorded over time spans greater than 30 years showing no significant change in character. We suggest that distinct differences in song provide another data set for comparison with genetic and morphological data when defining blue whale populations. Furthermore, we recommend that when there is a lack of other data, or lack of clarity in other data sets, evidence of distinct differences in songs between areas be used as the provisional population structure when making management decisions. Worldwide study is needed to better understand the various populations (subspecies) within species like the blue whale that have large geographic distributions and have both migrating and resident populations. The song types we propose here can be used to test various phylogeograp...

Springer Handbook of Auditory Research

ABSTRACT Acoustic models based on physics and mathematics may yield significant advances in the u... more ABSTRACT Acoustic models based on physics and mathematics may yield significant advances in the understanding of sound production, propagation, and interaction associated with whales and dolphins. Models can be used to estimate the limits of intensity and frequency that are physically possible given the anatomy of a species. Models can also tell us what kind of anatomical structures would be necessary in order to produce sound having specific characteristics. Models can be used to clarify what type of measurements should be performed to answer specific questions. Many areas of bioacoustics stand to benefit from simulation of sound propagation through biological tissues and the media surrounding them. However, accurate modeling of biological subjects with complex anatomical features is extremely challenging, and few modern studies exist of sound production and propagation in whales and dolphins.

Spatial and temporal patterns in visual and acoustic detection rates of blue whales in the southern California Bight

Oceans 2003. Celebrating the Past ... Teaming Toward the Future (IEEE Cat. No.03CH37492), 2003

... a time. Acoustic Recording Packages (ARPs) at Cortez and Tanner Banks have been acoustically ... more

Matched field geoacoustic tomography experiments using light bulb sound sources in the Haro Strait sea trial

ABSTRACT

Kinematics of foraging dives and lunge-feeding in fin whales

Journal of Experimental Biology, 2006

Ocean ambient noise in the North Atlantic during 1966 and 2013–2014

The Journal of the Acoustical Society of America, 2014

ABSTRACT

Seasonality of blue andfin whale calls andthe influence of sea ice in the Western Antarctic Peninsula

The calling seasonality of blue (Balaenoptera musculus) andfin ( B. physalus) whales was assessed... more The calling seasonality of blue (Balaenoptera musculus) andfin ( B. physalus) whales was assessedusing,acoustic data recorded on seven autonomous,acoustic recording packages,(ARPs) deployed,from March 2001 to February 2003 in the Western Antarctic Peninsula. Automatic,detection and,acoustic power,analysis methods,were used for determining presence and absence of whale calls. Blue whale calls were detected year round, on average 177 days per year, with

Calls recorded from North Pacific right whales ( Eubalaena japonica) in the eastern Bering Sea

Calls from North Pacific right whales ( Eubalaena,japonica) were recorded in the eastern Bering S... more Calls from North Pacific right whales ( Eubalaena,japonica) were recorded in the eastern Bering Sea during a visual and acoustic survey aboard the US Coast Guard buoy tender Sweetbrier, in July 1999. Calls were commonly detected to 20km, and in one case approximately 30km, via deployment of arrays of directional sonobuoys. Acoustic detections (clusters of right whale calls separated

BIOGEOGRAPHIC CHARACTERIZATION OF BLUE WHALE SONG WORLDWIDE: USING SONG TO IDENTIFY POPULATIONS

Blue whale songs provide a new means for characterizing blue whale population structure worldwide... more Blue whale songs provide a new means for characterizing blue whale population structure worldwide. These songs are divided into nine regional types, which maintain a stable character. Five of the nine song types have been recorded over time spans greater than 30 years showing no significant change in character. We suggest that distinct differences in song provide another data set

Seasonality of blue and fin whale calls west of the Antarctic Peninsula

Oceans 2003. Celebrating the Past ... Teaming Toward the Future (IEEE Cat. No.03CH37492), 2003

The calling seasonality of blue (Balaenoptera musculus) and fin (B. physalus) whales was assessed... more

A 50 Year comparison of ambient ocean noise near San Clemente Island: A bathymetrically complex coastal region off Southern California

The Journal of the Acoustical Society of America, 2008

Repeated ocean ambient noise measurements at a shallow water (110 m) site near San Clemente Islan... more Repeated ocean ambient noise measurements at a shallow water (110 m) site near San Clemente Island reveal little increase in noise levels in the absence of local ships. Navy reports document ambient noise levels at this site in 1958-1959 and 1963-1964 and a seafloor recorder documents noise during 2005-2006. When noise from local ships was excluded from the 2005-2006 recordings, median sound levels were essentially the same as were observed in 1958 and 1963. Local ship noise, however, was present in 31% of the recordings in 1963 but was present in 89% of the recordings in 2005-2006. Median levels including local ships are 6-9 dB higher than median levels chosen from times when local ship noise was absent. Biological sounds and the sound of wind driven waves controlled ambient noise levels in the absence of local ships. The median noise levels at this site are low for an open water site due to the poor acoustic propagation and low average wind speeds. The quiet nature of this site in the absence of local ships allows correlation of wind speed to wave noise across the 10-220 Hz spectral band of this study.

Sei whale sounds recorded in the Antarctic

The Journal of the Acoustical Society of America, 2005

Sei whales are the least well known acoustically of all the rorquals, with only two brief descrip... more Sei whales are the least well known acoustically of all the rorquals, with only two brief descriptions of their calls previously reported. Recordings of low-frequency tonal and frequency swept calls were made near a group of four or five sei whales in waters west of the Antarctic Peninsula on 19 February 2003. These whales also produced broadband sounds which can be described as growls or whooshes. Many of the tonal and frequency swept calls ͑30 out of 68͒ consist of multiple parts with a frequency step between the two parts, this being the most unique characteristic of the calls, allowing them to be distinguished from the calls of other whale species. The average duration of the tonal calls is 0.45± 0.3 s and the average frequency is 433± 192 Hz. Using a calibrated seafloor recorder to determine the absolute calibration of a sonobuoy system, the maximum source level of the tonal calls was 156± 3.6 dB re 1 Pa at 1 m. Each call had different character and there was no temporal pattern in the calling.

Acoustic current tomography of a coastal front in Haro Strait, British Columbia

by Mark McDonald and Pierre Elisseeff

The Journal of the Acoustical Society of America, 1996

Waveguide Propagation Allows Range Estimates for North Pacific Right Whales in the Bering Sea

Canadian Acoustics Acoustique Canadienne, 2004

The shallow and uniform water depth of the eastern Bering Sea shelf results in an acoustic wavegu... more The shallow and uniform water depth of the eastern Bering Sea shelf results in an acoustic waveguide. Propagation within this waveguide produces waveform dispersion which is dependent upon range. We present a means for using dispersed waveforms to determine range to calling whales from a single autonomous acoustic recording instrument. The predominant North Pacific right whale (Eubalaena japonica) call is frequency upswept from about 90 Hz to around 160 Hz and lasts approximately 1 s. The regional bathymetry of the eastern Bering Sea middle shelf is relatively uniform and shallow (~ 70 meters deep). This geometry provides a plane-layered waveguide in which right whale upswept calls can be detected at ranges over 50 km and have multiple modal arrivals that become dispersed, displaying different propagation velocities for different frequencies. Dispersion characteristics of modal arrivals are dependent on the calling whale's depth, the receiver's depth, the water depth, the range from caller to receiver, and various environmental parameters including water and sediment density and sound velocity. A model of sound propagation for the eastern Bering Sea middle shelf is developed from right whale call dispersion recorded on sonobuoys and seafloor acoustic recording packages, using individual calls recorded at multiple instruments. After development of the model, waveform dispersion allows estimation of caller range based on single instrument recordings. Estimating range between instrument and calling whales provides a means to estimate minimum abundance for the endangered North Pacific right whale.

Ocean ambient sound south of Bermuda and Panama Canal traffic

The Journal of the Acoustical Society of America, May 1, 2016

Comparisons of current and historic ocean ambient noise levels are rare, especially in the North ... more Comparisons of current and historic ocean ambient noise levels are rare, especially in the North Atlantic. Recent (2013-2014) monthly patterns in ocean ambient sound south of Bermuda were compared to those recorded at the same location in 1966. Additionally, trends in ocean traffic, in particular, Panama Canal traffic, over this time were also investigated. One year of ocean ambient noise measurements were collected in 1966 using cabled, omnidirectional hydrophones at the U.S. Navy Tudor Hill Laboratory in Bermuda, and repeat measurements were collected at the same location from June 2013-May 2014 using a High-frequency Acoustic Recording Package. Average monthly pressure spectrum levels at 44 Hz increased 2.8 ± 0.8 dB from 1966 to 2013, indicating an average increase of 0.6 dB/decade. This low level of increase may be due to topographic shielding at this site, limiting it to only southern exposure, and the limit in the number of ship transits through the Panama Canal, which did not...

Beaked Whale Presence, Habitat, and Sound Production in the North Pacific

Acoustic and Visual Detection of Large Whales in the Eastern North Pacific Ocean

Two cruises were conducted in the eastern North Pacific Ocean to investigate the precision of lar... more Two cruises were conducted in the eastern North Pacific Ocean to investigate the precision of large whale call locations as determined by the National Oceanic and Atmospheric Administration (NOAA) and Pacific Marine Environmental Laboratory's (PMEL) implementation of a localization and tracking routine using data from the U.S. Navy's Sound Surveillance System (SOSUS). Attempts to confirm SOSUS-derived large whale call locations by comparisons to standard vessel-based visual survey data were largely unsuccessful due to spatial and temporal differences in sampling scale.

Blue and fin whales observed on a seafloor array in the Northeast Pacific

Calling blue and fin whales have been tracked using relative travel times and amplitudes from bot... more Calling blue and fin whales have been tracked using relative travel times and amplitudes from both direct and multipath arrivals to a seafloor array of seismometers. Calls of three fin whales swimming in the same general direction, but several kilometers apart, are believed to represent communication between the whales because of signature differences in call character, an alternating call pattern, and coordination of call and respiration times. Whale call tracks, call patterns, call character, and swimming speeds were examined during periods with and without the presence of noise. Noise sources included airguns, when the whales were subject to sound levels of up to 143 dB P-P (peak-to-peak) re: 1 pPa over the 10 to 60-Hz band, and transits of merchant ships, when the whales received continuous levels up to 106 dB rms re: I /•Pa over the 10 to 60-Hz band (115 dB P-P). Whale responses associated with these noises remain arguable. ¸ 1995 Acoustical Society of America. PACS numbers: 43.80.Jz, 43.80.Ka, 43.80.Nd INTRODUCTION Many baleen whales produce loud low-frequency underwater sounds a significant percentage of the time, providing a practical tool with which to study whale distribution and movements (Watkins and Wartzok, 1985; Nishimura and Conlon, 1994; Clark, 1994). Studies of whales have used arrays of acoustic sensors to determine swimming speed and direction as well as to monitor call interaction between whales (Patterson and Hamilton, 1964; Cummings etal., 1968; Watkins and Schevill, 1977; Cummings and Holliday, 1985). Temporal patterns in acoustic call sequences provide a measure of respiration times (Cummings et al., 1986) while call characteristics may separate stocks or groups within the species (Winn et al., 1981; Ford and Fisher, 1983). Further study of whale calls may allow them to be used to monitor behavioral changes associated with man-made noise sources.

Microearthquakes at intermediate spreading-rate ridges: The Cleft segment megaplume site on the Juan de Fuca Ridge

... Kappel, ES and WR Normark (1987). Morphometric variability within the Axial Zone of the south... more

Mysticete whale acoustic and visual census in the SO GLOBEC West Antarctic Peninsula region

The distribution and relative abundance of mysticete whales in the SO GLOBEC West Antarctic Penin... more The distribution and relative abundance of mysticete whales in the SO GLOBEC West Antarctic Peninsula (WAP) region was investigated using acoustic and visual census techniques. Calls of three species (blue, fin and minke whales), recorded by autonomous acoustic recording packages (ARPs) were tallied for the period from April 2001 to February 2002. Blue and minke whale calls were recorded year-round, with calls from blue whales occurring far more frequently than those from minkes. Fin whale calls were strongly seasonal, with a peak in April-May 2001 and an absence of calls from July 2001 through January 2002. Calls from humpback whales were recorded on the ARPs but have not yet been tallied. Visual observations were conducted during eight SO GLOBEC cruises using standard line transect survey protocols, with resultant data confirming humpback and minke whale presence in the study region in austral autumn and winter. There was only one (possible) blue whale sighting and a few fin whale...

Biogeographic characterisation of blue whale song worldwide: Using song to identify populations

Journal of Cetacean Research and Management

Blue whale songs provide a new means for characterizing blue whale population structure worldwide... more Blue whale songs provide a new means for characterizing blue whale population structure worldwide. These songs are divided into nine regional types, which maintain a stable character. Five of the nine song types have been recorded over time spans greater than 30 years showing no significant change in character. We suggest that distinct differences in song provide another data set for comparison with genetic and morphological data when defining blue whale populations. Furthermore, we recommend that when there is a lack of other data, or lack of clarity in other data sets, evidence of distinct differences in songs between areas be used as the provisional population structure when making management decisions. Worldwide study is needed to better understand the various populations (subspecies) within species like the blue whale that have large geographic distributions and have both migrating and resident populations. The song types we propose here can be used to test various phylogeograp...

Springer Handbook of Auditory Research

ABSTRACT Acoustic models based on physics and mathematics may yield significant advances in the u... more ABSTRACT Acoustic models based on physics and mathematics may yield significant advances in the understanding of sound production, propagation, and interaction associated with whales and dolphins. Models can be used to estimate the limits of intensity and frequency that are physically possible given the anatomy of a species. Models can also tell us what kind of anatomical structures would be necessary in order to produce sound having specific characteristics. Models can be used to clarify what type of measurements should be performed to answer specific questions. Many areas of bioacoustics stand to benefit from simulation of sound propagation through biological tissues and the media surrounding them. However, accurate modeling of biological subjects with complex anatomical features is extremely challenging, and few modern studies exist of sound production and propagation in whales and dolphins.

Spatial and temporal patterns in visual and acoustic detection rates of blue whales in the southern California Bight

Oceans 2003. Celebrating the Past ... Teaming Toward the Future (IEEE Cat. No.03CH37492), 2003

... a time. Acoustic Recording Packages (ARPs) at Cortez and Tanner Banks have been acoustically ... more

Matched field geoacoustic tomography experiments using light bulb sound sources in the Haro Strait sea trial

ABSTRACT

Kinematics of foraging dives and lunge-feeding in fin whales

Journal of Experimental Biology, 2006

Ocean ambient noise in the North Atlantic during 1966 and 2013–2014

The Journal of the Acoustical Society of America, 2014

ABSTRACT

Seasonality of blue andfin whale calls andthe influence of sea ice in the Western Antarctic Peninsula

The calling seasonality of blue (Balaenoptera musculus) andfin ( B. physalus) whales was assessed... more The calling seasonality of blue (Balaenoptera musculus) andfin ( B. physalus) whales was assessedusing,acoustic data recorded on seven autonomous,acoustic recording packages,(ARPs) deployed,from March 2001 to February 2003 in the Western Antarctic Peninsula. Automatic,detection and,acoustic power,analysis methods,were used for determining presence and absence of whale calls. Blue whale calls were detected year round, on average 177 days per year, with

Calls recorded from North Pacific right whales ( Eubalaena japonica) in the eastern Bering Sea

Calls from North Pacific right whales ( Eubalaena,japonica) were recorded in the eastern Bering S... more Calls from North Pacific right whales ( Eubalaena,japonica) were recorded in the eastern Bering Sea during a visual and acoustic survey aboard the US Coast Guard buoy tender Sweetbrier, in July 1999. Calls were commonly detected to 20km, and in one case approximately 30km, via deployment of arrays of directional sonobuoys. Acoustic detections (clusters of right whale calls separated

BIOGEOGRAPHIC CHARACTERIZATION OF BLUE WHALE SONG WORLDWIDE: USING SONG TO IDENTIFY POPULATIONS

Blue whale songs provide a new means for characterizing blue whale population structure worldwide... more Blue whale songs provide a new means for characterizing blue whale population structure worldwide. These songs are divided into nine regional types, which maintain a stable character. Five of the nine song types have been recorded over time spans greater than 30 years showing no significant change in character. We suggest that distinct differences in song provide another data set

Seasonality of blue and fin whale calls west of the Antarctic Peninsula

Oceans 2003. Celebrating the Past ... Teaming Toward the Future (IEEE Cat. No.03CH37492), 2003

The calling seasonality of blue (Balaenoptera musculus) and fin (B. physalus) whales was assessed... more

A 50 Year comparison of ambient ocean noise near San Clemente Island: A bathymetrically complex coastal region off Southern California

The Journal of the Acoustical Society of America, 2008

Repeated ocean ambient noise measurements at a shallow water (110 m) site near San Clemente Islan... more Repeated ocean ambient noise measurements at a shallow water (110 m) site near San Clemente Island reveal little increase in noise levels in the absence of local ships. Navy reports document ambient noise levels at this site in 1958-1959 and 1963-1964 and a seafloor recorder documents noise during 2005-2006. When noise from local ships was excluded from the 2005-2006 recordings, median sound levels were essentially the same as were observed in 1958 and 1963. Local ship noise, however, was present in 31% of the recordings in 1963 but was present in 89% of the recordings in 2005-2006. Median levels including local ships are 6-9 dB higher than median levels chosen from times when local ship noise was absent. Biological sounds and the sound of wind driven waves controlled ambient noise levels in the absence of local ships. The median noise levels at this site are low for an open water site due to the poor acoustic propagation and low average wind speeds. The quiet nature of this site in the absence of local ships allows correlation of wind speed to wave noise across the 10-220 Hz spectral band of this study.

Sei whale sounds recorded in the Antarctic

The Journal of the Acoustical Society of America, 2005

Sei whales are the least well known acoustically of all the rorquals, with only two brief descrip... more Sei whales are the least well known acoustically of all the rorquals, with only two brief descriptions of their calls previously reported. Recordings of low-frequency tonal and frequency swept calls were made near a group of four or five sei whales in waters west of the Antarctic Peninsula on 19 February 2003. These whales also produced broadband sounds which can be described as growls or whooshes. Many of the tonal and frequency swept calls ͑30 out of 68͒ consist of multiple parts with a frequency step between the two parts, this being the most unique characteristic of the calls, allowing them to be distinguished from the calls of other whale species. The average duration of the tonal calls is 0.45± 0.3 s and the average frequency is 433± 192 Hz. Using a calibrated seafloor recorder to determine the absolute calibration of a sonobuoy system, the maximum source level of the tonal calls was 156± 3.6 dB re 1 Pa at 1 m. Each call had different character and there was no temporal pattern in the calling.

Acoustic current tomography of a coastal front in Haro Strait, British Columbia

by Mark McDonald and Pierre Elisseeff

The Journal of the Acoustical Society of America, 1996