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ABSTRACT: Dolphins are known to produce nearly omnidirectional whistles that can propagate several kilometers, allowing these sounds to be localized and tracked using acoustic arrays. During the fall of 2007, a km-scale array of four autonomous acoustic recorders was deployed offshore of southern California in a known dolphin habitat at ∼800 m depth. Concurrently with the one-month recording, a fixed-point marine mammal visual survey was conducted from a moored research platform in the center of the array, providing daytime species and behavior visual confirmation. The recordings showed three main types of dolphin acoustic activity during distinct times: primarily whistling during daytime, whistling and clicking during early night, and primarily clicking during late night. Tracks from periods of daytime whistling typically were tightly grouped and traveled at a moderate rate. In one example with visual observations, traveling common dolphins (Delphinus sp.) were tracked for about 10 km with an average speed of ∼2.5 m s(-1) (9 km h(-1)). Early night recordings had whistle localizations with wider spatial distribution and slower travel speed than daytime recordings, presumably associated with foraging behavior. Localization and tracking of dolphins over long periods has the potential to provide insight into their ecology, behavior, and potential response to stimuli.
The Journal of the Acoustical Society of America 06/2013; 133(6):3813-8. · 1.55 Impact Factor
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ABSTRACT: Echolocation signals from Baird's beaked whales were recorded during visual and acoustic shipboard surveys of cetaceans in the California Current ecosystem and with autonomous, long-term recorders in the Southern California Bight. The preliminary measurement of the visually validated Baird's beaked whale echolocation signals from towed array data were used as a basis for identifying Baird's signals in the autonomous recorder data. Two distinct signal types were found, one being a beaked whale-like frequency modulated (FM) pulse, the other being a dolphin-like broadband click. The median FM inter-pulse interval was 230 ms. Both signal types showed a consistent multi-peak structure in their spectra with peaks at ∼9, 16, 25, and 40 kHz. Depending on signal type, as well as recording aspect and distance to the hydrophone, these peaks varied in relative amplitude. The description of Baird's echolocation signals will allow for studies of their distribution and abundance using towed array data without associated visual sightings and from autonomous seafloor hydrophones.
The Journal of the Acoustical Society of America 06/2013; 133(6):4321-31. · 1.55 Impact Factor
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ABSTRACT: Low-frequency ocean ambient noise is dominated by noise from commercial ships, yet understanding how individual ships contribute deserves further investigation. This study develops and evaluates statistical models of container ship noise in relation to design characteristics, operational conditions, and oceanographic settings. Five-hundred ship passages and nineteen covariates were used to build generalized additive models. Opportunistic acoustic measurements of ships transiting offshore California were collected using seafloor acoustic recorders. A 5-10 dB range in broadband source level was found for ships depending on the transit conditions. For a ship recorded multiple times traveling at different speeds, cumulative noise was lowest at 8 knots, 65% reduction in operational speed. Models with highest predictive power, in order of selection, included ship speed, size, and time of year. Uncertainty in source depth and propagation affected model fit. These results provide insight on the conditions that produce higher levels of underwater noise from container ships.
Scientific Reports 05/2013; 3:1760.
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ABSTRACT: U.S. Coast Guard Cutter Healy's underwater radiated noise signature was characterized in the central Arctic Ocean during different types of ice-breaking operations. Propulsion modes included transit in variable ice cover, breaking heavy ice with backing-and-ramming maneuvers, and dynamic positioning with the bow thruster in operation. Compared to open-water transit, Healy's noise signature increased approximately 10 dB between 20 Hz and 2 kHz when breaking ice. The highest noise levels resulted while the ship was engaged in backing-and-ramming maneuvers, owing to cavitation when operating the propellers astern or in opposing directions. In frequency bands centered near 10, 50, and 100 Hz, source levels reached 190-200 dB re: 1 μPa at 1 m (full octave band) during ice-breaking operations.
The Journal of the Acoustical Society of America 04/2013; 133(4):1971-80. · 1.55 Impact Factor
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ABSTRACT: Killer whales in the North Pacific, similar to Atlantic populations, produce high-frequency modulated signals, based on acoustic recordings from ship-based hydrophone arrays and autonomous recorders at multiple locations. The median peak frequency of these signals ranged from 19.6-36.1 kHz and median duration ranged from 50-163 ms. Source levels were 185-193 dB peak-to-peak re: 1 μPa at 1 m. These uniform, repetitive, down-swept signals are similar to bat echolocation signals and possibly could have echolocation functionality. A large geographic range of occurrence suggests that different killer whale ecotypes may utilize these signals.
The Journal of the Acoustical Society of America 04/2012; 131(4):EL295-301. · 1.55 Impact Factor
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ABSTRACT: Anthropogenic noise may significantly impact exposed marine mammals. This work studied the vocalization response of endangered blue whales to anthropogenic noise sources in the mid-frequency range using passive acoustic monitoring in the Southern California Bight. Blue whales were less likely to produce calls when mid-frequency active sonar was present. This reduction was more pronounced when the sonar source was closer to the animal, at higher sound levels. The animals were equally likely to stop calling at any time of day, showing no diel pattern in their sensitivity to sonar. Conversely, the likelihood of whales emitting calls increased when ship sounds were nearby. Whales did not show a differential response to ship noise as a function of the time of the day either. These results demonstrate that anthropogenic noise, even at frequencies well above the blue whales' sound production range, has a strong probability of eliciting changes in vocal behavior. The long-term implications of disruption in call production to blue whale foraging and other behaviors are currently not well understood.
PLoS ONE 01/2012; 7(2):e32681. · 4.09 Impact Factor
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ABSTRACT: Underwater radiated noise measurements for seven types of modern commercial ships during normal operating conditions are presented. Calibrated acoustic data (<1000 Hz) from an autonomous seafloor-mounted acoustic recorder were combined with ship passage information from the Automatic Identification System. This approach allowed for detailed measurements (i.e., source level, sound exposure level, and transmission range) on ships of opportunity. A key result was different acoustic levels and spectral shapes observed from different ship-types. A 54 kGT container ship had the highest broadband source level at 188 dB re 1 μPa@1m; a 26 kGT chemical tanker had the lowest at 177 dB re 1 μPa@1m. Bulk carriers had higher source levels near 100 Hz, while container ship and tanker noise was predominantly below 40 Hz. Simple models to predict source levels of modern merchant ships as a group from particular ship characteristics (e.g., length, gross tonnage, and speed) were not possible given individual ship-type differences. Furthermore, ship noise was observed to radiate asymmetrically. Stern aspect noise levels are 5 to 10 dB higher than bow aspect noise levels. Collectively, these results emphasize the importance of including modern ship-types in quantifying shipping noise for predictive models of global, regional, and local marine environments.
The Journal of the Acoustical Society of America 01/2012; 131(1):92-103. · 1.55 Impact Factor
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ABSTRACT: From September 2006 to June 2009, an autonomous acoustic recorder measured ambient noise north of Barrow, Alaska on the continental slope at 235 m depth, between the Chukchi and Beaufort Seas. Mean monthly spectrum levels, selected to exclude impulsive events, show that months with open-water had the highest noise levels (80-83 dB re: 1 μPa(2)/Hz at 20-50 Hz), months with ice coverage had lower spectral levels (70 dB at 50 Hz), and months with both ice cover and low wind speeds had the lowest noise levels (65 dB at 50 Hz). During ice covered periods in winter-spring there was significant transient energy between 10 and 100 Hz from ice fracture events. During ice covered periods in late spring there were significantly fewer transient events. Ambient noise increased with wind speed by ~ 1 dB/m/s for relatively open-water (0%-25% ice cover) and by ~ 0.5 dB/m/s for nearly complete ice cover (> 75%). In September and early October for all years, mean noise levels were elevated by 2-8 dB due to the presence of seismic surveys in the Chukchi and Beaufort Seas.
The Journal of the Acoustical Society of America 01/2012; 131(1):104-103. · 1.55 Impact Factor
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ABSTRACT: To track highly directional echolocation clicks from odontocetes, passive hydrophone arrays with small apertures can be used to receive the same high frequency click on each sensor. A four-hydrophone small-aperture array was coupled to an autonomous acoustic recorder and used for long-term tracking of high-frequency odontocete sounds. The instrument was deployed in the spring of 2009 offshore of southern California in a known beaked whale and dolphin habitat at about 1000 m depth. The array was configured as a tetrahedron with approximately 0.5 m sensor spacing. Time difference of arrival measurements between the six sensor-pairs were used to estimate three-dimensional bearings to sources. Both near-seafloor beaked whales and near-sea surface dolphins were tracked. The tracks observed using this technique provide swimming and diving behavioral information for free-ranging animals using a single instrument. Furthermore, animal detection ranges were derived, allowing for estimation of detection probability functions.
The Journal of the Acoustical Society of America 01/2012; 131(1):156-63. · 1.55 Impact Factor
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ABSTRACT: Tracking marine mammals over long periods can provide information on their movement patterns including base-line behavior and responses to natural and anthropogenic stimuli. Autonomous acoustic recorders provide a cost effective and portable means of tracking these sounds over long periods, but until recently these devices have been restricted to tracking low-frequency large whales because of limited recording capabilities. In this paper, we will present long-term, passive acoustic tracking of high-frequency dolphin whistles and clicks using autonomous hydrophone recording arrays with kilometer- and meter-scale apertures.
The Journal of the Acoustical Society of America 10/2011; 130(4):2322. · 1.55 Impact Factor
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ABSTRACT: Killer whales (Orcinus orca) use acoustic signals to echolocate and communicate, although there are differences in acoustic behavior among ecotypes. Atlantic resident populations recently have been reported to produce acoustic signals at higher frequencies than previously known. Acoustic recordings from ship-based acoustic and visual surveys and from autonomous acoustic recorders reveal that killer whales across a broad range of the North Pacific Ocean also use similar high frequency modulated signals. The median peak frequency of these signals ranged from 19.6 to 36.1 kHz at different locations, with median durations from each location ranging from 50 to 163 ms. All observed high frequency modulated signals were frequency downswept with no or few inflection points. Killer whales are generally believed to use whistles for close range communication in social contexts; however, these uniform, repetitive, down-swept signals are similar to bat echolocation signals and may have echolocation functionality. The large geographic range of occurrence suggests that these signals are utilized by different killer whale ecotypes. [Work funded by Michael Weise at the Office of Naval Research, Frank Stone at Navy CNO-N45, Bob Haskell at Pacific Life, and Mark Spaulding at the Ocean Foundation.].
The Journal of the Acoustical Society of America 10/2011; 130(4):2322. · 1.55 Impact Factor
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ABSTRACT: Marine mammals produce a wide range of frequency-modulated sounds at low and high frequencies as well as directional broadband echolocation sounds in a refractive ocean environment. This creates several challenges for passive acoustic long-term tracking of the various marine mammal species. To overcome these, three-dimensional small-aperture hydrophone arrays coupled to seafloor multi-channel recording packages were deployed in a large aperture array in the Southern California Bight. Taking advantage of the experimental setup in the oceanic waveguide, time and frequency-domain tracking methods will be presented and tracks of marine mammals as well as anthropogenic sources will be shown. This provides a tool to study over long timescales behavioral responses of tracked marine mammals to tracked anthropogenic sources.
The Journal of the Acoustical Society of America 10/2011; 130(4):2378. · 1.55 Impact Factor
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ABSTRACT: While over 100 fish families produce sounds during behaviors like spawning, aggression, and feeding, passive-acoustic sampling is not used commonly for long-term fish population monitoring. Fish sounds consist mostly of low-frequency pulses of variable duration, number, and repetition rate, but it is often difficult to identify their sources to species. For example, underwater sounds from marine life have been studied in the Southern California Bight (SCB) for over 60 years, but because the sound producing fishes are difficult to locate and identify visually, their sound production remains poorly understood. The spatial and temporal distributions of the likely fish sounds recorded in SCB were analyzed, but the species producing those sounds are generally unknown. Where the species are known, more information is needed on the seasonal and interannual variations of their sound production if the passive-acoustic records are to be used to estimate their abundances and distributions. We show that sound characteristics and diel sound production patterns for some species, like bocaccio (Sebastes paucispinis), have not changed for over four decades. More directed studies are needed on the behavioral context of fish sound production in SCB to facilitate the use of passive-acoustic monitoring for long-term studies of fish population dynamics.
The Journal of the Acoustical Society of America 10/2011; 130(4):2499. · 1.55 Impact Factor
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ABSTRACT: Marine ambient sound was recorded on autonomous high-frequency acoustic recording packages (bandwidth 10 Hz to 100 kHz) during long term deployments at multiple sites across the North Pacific, from the high latitude Aleutian Islands to tropical Palmyra Atoll in depths of 600-1 000 m. Most intertropical but no temperate locations showed a distinct diel pattern in ambient sound. The soundscape at each location was unique, yet there was a similar recurring sound of unknown origin in lower latitude locations. This sound had a peak frequency around 3-5 kHz and was recorded only for several hours after sunset. Additionally, at some locations, a broadband acoustic signal with bandwidth up to 60 kHz was recorded at night with crepuscular peaks. Both sound patterns were lunar dependent with lower acoustic levels during full moon phases. Site-specific diel and seasonal acoustic patterns have been observed for various odontocete species. Correlations between odontocete presence and levels of ambient sound are investigated. [Work supported by NOAA-Pacific Islands Fisheries Science Center, US Navy-N45/PACFLT, ONR, Pacific Life, Ocean Foundation, University of California, San Diego.].
The Journal of the Acoustical Society of America 10/2011; 130(4):2536. · 1.55 Impact Factor
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ABSTRACT: High-Frequency Acoustic Recording Packages (HARPs) continuously monitored delphinids at five sites in the northeastern Gulf of Mexico during and after the Deepwater Horizon oil spill. Surface oil reached two sites, while the three unexposed sites functioned as "controls." Presence of dolphin vocalizations (clicks, whistles, and burst pulses) was documented at exposed and unexposed sites over the course of a year following the oil spill. These sites are within the known habitat ranges of 11 species of delphinids. Broadband towed array recordings with visual identifications were used to determine species-specific vocalization characteristics, which were then compared with autonomously recorded vocalizations. Two species have distinctive vocalizations that match between towed array and autonomous recordings. At least four more unique vocalization patterns were detected autonomously, which may be species-specific. Both clicks and whistles were explored for identifying features. The data provide a comparative view of delphinid presence relative to the oil spill.
The Journal of the Acoustical Society of America 10/2011; 130(4):2537. · 1.55 Impact Factor
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ABSTRACT: The Deepwater Horizon oil spill during the summer of 2010 impacted a region of sperm whale habitat along the continental slope and deep waters of the Gulf of Mexico. Passive acoustic monitoring was used to study the potential impact of the oil spill on sperm whales by recording trends in their characteristic sounds, such as echolocation clicks and foraging creaks. High-frequency Acoustic Recording Packages (HARPs) were deployed shortly after the oil spill began; one was located close to the Deepwater Horizon well, above which the sea surface was contaminated by oil throughout the summer of 2010, and another was deployed in a region of sperm whale habitat that remained unexposed to surface oil to function as a "control" site. At both sites, sperm whales were detected on a majority of days during the nearly year-long recording period. Sperm whale presence was evaluated from detected clicks and creaks, and changes in these sounds over time and between sites were compared.
The Journal of the Acoustical Society of America 10/2011; 130(4):2537. · 1.55 Impact Factor
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ABSTRACT: For the purposes of describing and understanding ambient sea noise for frequencies below about 300 Hz, most of the world's seas can be classified as belonging to one of three bathymetric domains. These domains are distinguished by their proximity to shipping lanes and by the degree to which they are exposed to noises originating at long distances. The three domains display different short-term characteristics as well as different historical patterns. In this paper, the three domains are described and typical ambient noise characteristics for each are shown, including changes which are attributable to increased ocean commerce.
The Journal of the Acoustical Society of America 10/2011; 130(4):2557. · 1.55 Impact Factor
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ABSTRACT: Underwater ambient noise levels measured off the coast of southern California were correlated with regional changes in commercial shipping trade. Between 2007 and 2010, two events occurred that resulted in a decrease in ship traffic in the Santa Barbara Channel: the economic recession and a coastal air-quality improvement rule. From October 2005 to June 2010, monthly low-frequency ambient noise levels at a site 3 km from a major shipping route were compared to regional traffic levels. Two different metrics of ship traffic showed that on average a 1 dB reduction in low-frequency noise levels resulted from a decrease in traffic by one ship passage per day in a coastal basin.
The Journal of the Acoustical Society of America 10/2011; 130(4):2557. · 1.55 Impact Factor
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ABSTRACT: The vocalizations of migrating eastern North Pacific gray whales (Eschrichtius robustus) are not well understood, but studying these sounds may provide insights to their behaviors and encounters along their migratory route. To record migratory gray whale sounds over long periods, a high frequency acoustic recording package (HARP) was deployed from March to May 2010 off the north coast of the Santa Barbara Channel, an area where the gray whale northbound migration is close to shore. The HARP recorded continuously and concurrently with a shore-based visual survey of marine mammals. Comparisons of calls and sightings were conducted to relate calling repertoires with various types of migrating whale behaviors and groups (e.g., cow/calf pairs, juveniles, etc.). The spatial and temporal overlap of the visual and acoustic data enabled the estimation of call detection ranges and source levels. Characterization of gray whale vocalizations also will help with the development of automatic detectors which will aid in future the investigations of long-term gray whale recordings, including potential responses to anthropogenic activity.
The Journal of the Acoustical Society of America 10/2011; 130(4):2561. · 1.55 Impact Factor
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ABSTRACT: In 2007 it was proposed that the U.S. Navy's Quinault Underwater Tracking Range (QUTR) off the outer Washington coast be expanded into deep water habitats (used by beaked and sperm whales) and along the coastal shelf (where coastal cetaceans forage). In 2004 an acoustic and visual monitoring effort was initiated within the boundaries of the expanded QUTR to characterize the vocalizations of marine mammal species present in the area, to determine the year-round seasonal presence of all odontocete and mysticete whales, and to evaluate the distribution of cetaceans near the Navy range. Acoustic data have been collected at two sites using autonomous High-frequency Acoustic Recording Packages (HARPs). This report summarizes acoustic data collected from June 2008 to June 2009. Seasonal occurrence and relative abundance of species consistently identified in the acoustic data are discussed in the context of earlier visual and acoustic data collections.
07/2011;
