Joal J Newcomb

University of New Orleans, New Orleans, Louisiana, United States

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Publications (23)23.04 Total impact

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    ABSTRACT: The Littoral Acoustic Demonstration Center conducted the Source Characterization Study in 2007 (SCS07) to measure the 3-D acoustic field of a seismic airgun array in the Gulf of Mexico. Three moorings with sensitive and desensitized hydrophones at different depths were deployed as well as hydrophones suspended from a ship, while a seismic source vessel shot specified lines. Hydrophone positions were measured. Peak pressures, RMS sound pressure levels (SPL), sound exposure levels, total shot energy spectra, one-third octave band analyses, and source directivity studies are used to characterize the field. Summary results are first calculated for each hydrophone. These are then combined to give isopleths for azimuthal cuts at 0, 45, 90 degrees, etc., for the spatial domain measures. Plots for each solid angle bin give these and frequency measures analyzed versus range. Zero-to-peak pressures directly under the array go from 210 dB for depths less than 200 m down to 195 dB at 1200 m. At 2000 m horizontal range the pressures go from 160 dB near the surface to 175 to 180 dB at 1200 m. RMS SPL is about 5 dB smaller. [Research supported by the Joint Industry Programme through the International Association of Oil and Gas Producers.].
    The Journal of the Acoustical Society of America 11/2013; 134(5):4113. · 1.65 Impact Factor
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    ABSTRACT: The Littoral Acoustic Demonstration Center has conducted an experiment to measure the 3-D acoustic field of a seismic airgun array in the Gulf of Mexico. A seismic source vessel shot specified lines to give solid angle and range information. Hydrophone positions were measured by an ultra-short baseline (USBL) acoustic system while the source ship was turning between lines. An acoustic Doppler current profiler measured currents so the positions could be modeled between USBL measurements. The position locations were refined by using information from the acoustic arrival times on the hydrophones. Peak pressures, sound exposure levels, total shot energy spectra, one-third octave band analyses, and source directivity studies are used to characterize the field. One third octave band analysis shows received levels up to 180 dB re 1 [micro sign]P for emission angles from 0 degrees (vertically down) up to 45 degrees for horizontal ranges up to 200 m at endfire, between 10 Hz and 200 Hz. The levels decrease with increasing frequency above 200 Hz, with increasing horizontal ranges, and for emission angles above 45 degrees. The levels are lower at broadside than at endfire. [Research supported by the Joint Industry Programme through the International Association of Oil and Gas Producers.].
    The Journal of the Acoustical Society of America 09/2012; 132(3):2056. · 1.65 Impact Factor
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    ABSTRACT: Long-term monitoring of endangered species abundance based on acoustic recordings has not yet been pursued. This paper reports the first attempt to use multi-year passive acoustic data to study the impact of the Deepwater Horizon oil spill on the population of endangered sperm whales. Prior to the spill the Littoral Acoustic Demonstration Center (LADC) collected acoustic recordings near the spill site in 2007. These baseline data now provide a unique opportunity to better understand how the oil spill affected marine mammals in the Gulf of Mexico. In September 2010, LADC redeployed recording buoys at previously used locations 9, 25, and 50 miles away from the incident site. A statistical methodology that provides point and interval estimates of the abundance of the sperm whale population at the two nearest sites is presented. A comparison of the 2007 and the 2010 recordings shows a decrease in acoustic activity and abundance of sperm whales at the 9-mile site by a factor of 2, whereas acoustic activity and abundance at the 25-mile site has clearly increased. This indicates that some sperm whales may have relocated farther away from the spill. Follow-up experiments will be important for understanding long-term impact.
    The Journal of the Acoustical Society of America 03/2012; 131(3):2306-14. · 1.65 Impact Factor
  • The Journal of the Acoustical Society of America 01/2011; 129. · 1.65 Impact Factor
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    ABSTRACT: The Source Characterization Study 2007 (SCS07) measured the three-dimensional (3-D) acoustic field of a seismic airgun array. The Littoral Acoustic Demonstration Center (LADC) performed the experiment, collecting acoustic and related data on three moored hydrophone arrays and one ship-deployed hydrophone array which together spanned the full water column. Sensitive and desensitized phones were deployed at each position to extend the dynamic range. An ultra short baseline localization system was deployed with the EARS moorings to provide array shape. With postanalysis this results in time-dependent positions for each of the acoustic sensors. Every channel is calibrated. A seismic source vessel shot a series of lines designed to give detailed angle and range information concerning the field of the primary arrival. Peak pressures, sound exposure levels, total shot energy spectra, and one-third octave band analyses give important insights into details of the acoustic field. Images of these quantities are generated to show dependence on emission and azimuthal angles and range. 3-D visualizations and two-dimensional cuts through the data are shown. [Research supported by the Joint Industry Programme through the International Association of Oil and Gas Producers.].
    The Journal of the Acoustical Society of America 03/2010; 127(3):1787. · 1.65 Impact Factor
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    ABSTRACT: Littoral Acoustic Demonstration Center (LADC) scientists have investigated sperm and beaked whale clicks as recorded on Environmental Acoustic Recording System (EARS) buoys to analyze whale behavior and the possibility of identifying individual whales acoustically. The research began in 2001 and continues through the present. LADC has conducted three experiments in the northern Gulf of Mexico and participated with the Naval Undersea Research Centre with three experiments in the Ligurian Sea. Initially the research centered on sperm whale coda clicks and echolocation clicks. In 2007 it was extended to the study of beaked whale echolocation clicks. The measured data suggest that click properties can be used to identify individual whales. Initially the identifications were done by grouping clicks using self-organizing maps and other means of cluster analysis. Each cluster or class represents an individual whale. These methods have been refined and have become reasonably robust. Verification of the identification has been a problem since using visual observations has not been satisfactory. Presently localization of the clicking animals is being coupled with cluster analysis to verify the identifications. A new finding that rhythms of echolocation clicks can be used to identify sperm whale individuals is now a part of the research, and cluster analysis, rhythm analysis, and localization are mutually reinforcing the identifications. Other results using EARS buoys for marine animal acoustics are listed among the key findings of LADC acoustic research.
    OCEANS 2009, MTS/IEEE Biloxi - Marine Technology for Our Future: Global and Local Challenges; 11/2009
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    ABSTRACT: In September 2007 the Littoral Acoustic Demonstration Center (LADC), a consortium of University and Navy scientists, conducted an experiment in the northwest Gulf of Mexico to measure the three-dimensional acoustic field of the primary arrival from a seismic airgun array. The water depth was approximately 1500 m. The acoustic measurements were made by Generation 2 4-channel EARS (Environmental Acoustic Recording System) buoys developed by the Naval Oceanographic Office (NAVOCEANO), with each channel capable of measuring to 25 kHz. A total of 48 hydrophones were deployed on 3 moorings at 20 different depths. At each depth there was a sensitive and desensitized phone, the latter used to prevent clipping. Eight hydrophones (four pairs) were ship-deployed near the surface. A dedicated source ship, the M/V Fairfield ENDEAVOR, supplied almost all the shots, although the M/V Veritas VANTAGE, which was conducting a survey in the area, provided a few lines of opportunity. The M/V CAPE HATTERAS was used to deploy, manage, and recover the receiving hydrophone arrays, as well as to conduct all environmental measurements. It also deployed and provided communication and control for the Ultra Short BaseLine Localization (USBL) system and a single Acoustic Doppler Current Profiler (ADCP), which were used to give accurate hydrophone positions during the experiment. About 3.5 TB of data were collected.
    OCEANS 2009, MTS/IEEE Biloxi - Marine Technology for Our Future: Global and Local Challenges; 11/2009
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    ABSTRACT: Previous research to identify individual sperm and beaked whales from the properties of their echolocation and coda clicks using cluster analysis has been reported. Although reasonably consistent and robust results showing distinct classes (each corresponding to an individual) have been obtained with both self-organizing maps and K-means, no independent verification of these identifications has previously been available. However, data from a July 2007 experiment in the Gulf of Mexico should provide enough geometry information to verify some identifications. The Littoral Acoustic Demonstration Center deployed six environmental acoustic recording system buoys, measuring to 96 kHz for 9 days, to record sperm and beaked whale clicks in the northern Gulf of Mexico. Three buoys were in close proximity to enable multisensor detections of single clicks for possible localization, tracking, or bearing estimation sufficient to confirm the identification of individuals from cluster analysis. Displays of cluster classifications versus time coupled with location estimates for the clicks give evidence of the accuracy of the identifications. Though localization serves to verify the classification tool, click identification complements localization by separating sounds from multiple sources when several whales' clicktrains overlap, potentially enabling previously impossible tracking. [Research supported by SPAWAR and ONR.].
    The Journal of the Acoustical Society of America 05/2009; 125(4):2616. · 1.65 Impact Factor
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    ABSTRACT: EARS buoys were developed as autonomous, moored, underwater recording systems by the Naval Oceanographic Office (NAVOCEANO) to make long-term ocean ambient noise measurements. When the Littoral Acoustic Demonstration Center (LADC) was formed as a consortium of university and U.S. Navy scientists in 2001, the buoys were capable of measuring up to 1000 Hz for 1 yr. LADC added listening to sperm whales to its noise and propagation measurements. NAVOCEANO quickly modified the buoys to measure up to 5859 Hz for 36 days. The buoys, moored at depths from 550 to 950 m in the Gulf of Mexico, produced exceptionally clear recordings of sperm whale echolocation and coda clicks and recordings of other whales. EARS Generation 2 buoys are now capable of recording one channel to 96 kHz, or four channels to 25 kHz, for more than 13 days on four 120 Gbyte notebook disk drives. Experiments in the Gulf of Mexico and the Ligurian Sea have targeted both sperm and beaked whales. Audio results and visualizations of these recordings reveal rich detail of Odontocete clicks and enable new analyses, such as the identification of individual whales from the properties of their clicks. [Research supported by ONR and SPAWAR.].
    The Journal of the Acoustical Society of America 05/2009; 125(4):2616. · 1.65 Impact Factor
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    ABSTRACT: During September 2007 the Littoral Acoustic Demonstration Center collected acoustic and related data from three moored arrays and ship-deployed hydrophones spanning the full water column to measure the 3-D acoustic field of a seismic airgun array. A seismic source vessel shot a series of lines to give detailed angle and range information concerning the field of the primary arrival. The data were collected in the western Gulf of Mexico between the East Break and Alamos Canyon regions. Peak pressures, sound exposure levels, total energy spectra, one-third octave band, and source directivity analyses are measures used to characterize the field. Three-dimensional maps of these quantities are generated to show dependence on emission and azimuthal angles and range. Three-dimensional visualizations are being developed using a visualization cave and software for 2-D cave emulation. [Research supported by the Joint Industry Programme through the International Association of Oil and Gas Producers.].
    The Journal of the Acoustical Society of America 05/2009; 125(4):2539. · 1.65 Impact Factor
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    ABSTRACT: In September 2007 the Littoral Acoustic Demonstration Center (LADC) collected acoustic and related data from three moored arrays and ship-deployed hydrophones spanning the full water column to measure the three-dimensional acoustic field of a seismic airgun array. The seismic source vessel shot a series of lines to give a detailed angle and range information concerning the field. The data were collected in the western Gulf of Mexico between the East Break and Alamos Canyon regions. Peak pressures, sound exposure levels, total shot energy spectra, and one-third octave band analyses are measures used to characterize the field. Three dimensional maps of these quantities are generated to show dependence on emission and azimuthal angles and range. Both the direct and indirect fields are characterized. Moveout analysis is done to delineate arrivals and to detect ducted and interface waves. [Research supported by the International Association of Oil and Gas Producers.].
    The Journal of the Acoustical Society of America 11/2008; 124(4):2599. · 1.65 Impact Factor
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    ABSTRACT: In the summer of 2003, the Littoral Acoustic Demonstration Center conducted an acoustic characterization experiment for a 21-element marine seismic exploration airgun array of total volume of 0.0588 m(3) (3590 in.(3)). Two Environmental Acoustic Recording System buoys, one with a desensitized hydrophone, were deployed at a depth of 758 m in a water depth of 990 m, near Green's Canyon in the Gulf of Mexico. Shots over a grid were recorded and calibrated to produce absolute broadband (up to 25 kHz) pressure-time dependencies for a wide range of offsets and arrival angles in the water column. Experimental data are analyzed to obtain maximum received zero-to-peak pressure levels, maximum received sound exposure levels, and pressure levels in 13-octave frequency bands for each shot. Experimental data are quantitatively modeled by using an upgraded version of an underwater acoustic propagation model and seismic source modeling packages for a variety of ranges and arrival angles. Experimental and modeled data show good agreement in absolute pressure amplitudes and frequency interference patterns for frequencies up to 1000 Hz. The analysis is important for investigating the potential impact on marine mammals and fish and predicting the exposure levels for newly planned seismic surveys in other geographic areas.
    The Journal of the Acoustical Society of America 07/2008; 123(6):4094-108. · 1.65 Impact Factor
  • The Journal of the Acoustical Society of America 01/2007; 122(5). · 1.65 Impact Factor
  • SEG Technical Program Expanded Abstracts 01/2006; 25(1).
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    ABSTRACT: In the summer of 2003 two Environmental Acoustic Recording System (EARS) buoys were deployed in the northern Gulf of Mexico by the Littoral Acoustic Demonstration Center. The buoys were collocated and recorded ambient noise and seismic airgun array shots up to approximately 25 kHz. The gains and hydrophone sensitivities were set such that one EARS buoy could record the seismic shots without clipping and the other could record ambient noise. The M/V Kondor towed an airgun array on parallel linear tracks with horizontal closest points of approach to the buoy of 0, 500, 1000, 2000, and 5000 m, giving experimental data for a wide range of horizontal distances (up to 7 km) and arrival angles. The raw data were calibrated using the EARS system parameters to produce calibrated pressure time series for each shot. These data are analyzed in both the time and frequency domains. Maximum pressures for each shot as well as sound exposure levels (pressure squared integrated over time for 200 ms in this case) are presented. Also presented is a spectrogram analysis. The maximum time-domain peak pressure recorded is 200 dB re: 1 [mu]Pa. The maximum sound exposure level is 177 dB re: 1 [mu]Pa2 s. [Research supported by Industry Research Funding Coalition.]
    The Journal of the Acoustical Society of America 10/2005; · 1.65 Impact Factor
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    ABSTRACT: The Littoral Acoustic Demonstration Center (LA DC) deployed three Environmental Acoustic Recording System (EARS) buoys in the northern Gulf of Mexico during the summers of 2001 (LADC 01) and 2002 (LADC 02). The hydrophone of each buoy was approximately 50m from the bottom in water depths of 645m to 1034m. During LADC 01 Tropical Storm Barry passed within 93nmi east of the EARS buoys. During LADC 02 Tropical Storm Isidore and Hurricane Lili passed within approximately 73nmi and 116nmi, respectively, west of the EARS buoys. The proximity of these storm systems to the EARS buoys, in conjunction with wind speed data from three nearby NDBC weather buoys, allows for the direct comparison of underwater ambient noise levels with high wind speeds. These results are compared to the G. M. Wenz spectra at frequencies from 1kHz to 5.5kHz. In addition, the impact of storm conditions on sperm whale clicks was assessed. In particular, although the time period during the closest approach of TS Barry tended to produce lower click rates, this time period did not have the greatest incidence of non-detection at all the EARS buoys. It follows that storm-related masking noise could not have been responsible for all the observed trends. The data suggest that sperm whales may have left the vicinity of the deepest EARS buoy (nearest TS Barry's storm track) during the storm and possibly moved into the shallower waters around the other EARS buoys. It also appears that sperm whales may not have returned to the deepest EARS area, or did not resume normal behavior immediately after the storm, as the click rate did not recover to pre-storm levels during the period after TS Barry had dissipated. Results of these analyses and the ambient noise analysis will be presented. (Research supported by ONR).
    01/2004;
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    ABSTRACT: The Littoral Acoustic Demonstration Center (LADC) deployed three environmental and acoustic moorings in a downslope line just off the Mississippi River Delta in the northern Gulf of Mexico in an area of a large concentration of sperm whales in July 2001. The measurement of whale vocalizations and, more generally, ambient noise, were the objectives of the experiment. Each mooring had a single hydrophone autonomously recording Environmental Acoustic Recording System (EARS) obtained from the U.S. Naval Oceanographic Office and modified to recorded signals up to 5859 Hz continuously for 36 days. Also, self-recording, environmental sensors were attached to the moorings to obtain profiles of time series data of temperature and salinity. Satellite imagery and NOAA mooring data were gathered for an analysis of eddy formations and movement in the Gulf. This paper will discuss the possible environmental impact of two events that occurred during the experiment: the passage of Tropical Storm Barry and the movement of the remnants of an eddy in the area. Discussed also will be the expected effects of these events on acoustic propagation based on modeling, which are carried out for long range and low frequency (300 km and 500 Hz) using the normal-mode acoustic model SWAMP (Shallow Water Acoustic Modal Propagation by M. F. Werby and N. A. Sidorovskaia) and for short range and high frequency (10 km and 5000 Hz) using the parabolic-equation acoustic model RAM (Range-dependent Acoustic model by M. Collins). [Work supported by ONR.]
    The Journal of the Acoustical Society of America 01/2003; 113:2332-2332. · 1.65 Impact Factor
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    ABSTRACT: During August 2002, the Littoral Acoustic Demonstration Center (LADC) deployed three Environmental Acoustic Recording System (EARS) buoys, at approximately the same location in the northern Gulf of Mexico, in water depths of 645 m to 1034 m. The hydrophone of each buoy was approximately 50 m from the bottom. During the experiment, Hurricane Lili passed within approximately 116 nautical miles west of the EARS buoys. The proximity of this hurricane to the EARS buoys, in conjunction with wind speed data from three nearby NOAA weather buoys, allows for the direct correlation of underwater ambient noise with wind speed. During hurricane conditions, it is expected that the noise contribution due to local shipping would be absent. Time-series data from the shallowest and the deepest of the EARS buoys were processed to yield calibrated spectral levels. These spectra are compared to corresponding spectra derived from Wenz. In the wind-dependent frequency range, a general consistency of agreement is observed in spectral shape with the Wenz spectra and the calibrated spectral levels. General consistency is also observed with the NOAA buoy data and Beaufort scale estimates. Shallow water noise levels are generally higher than temporally corresponding deep-water levels. [Research supported by ONR.]
    Journal of The Acoustical Society of America - J ACOUST SOC AMER. 01/2003; 114:2463-2463.
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    ABSTRACT: The Littoral Acoustic Demonstration Center (LADC) consisting of the University of Southern Mississippi (USM), the University of New Orleans (UNO), and the Naval Research Laboratory at Stennis Space Center (NRL-SSC), with guidance and technical assistance from the Naval Oceanographic Office (NAVOCEANO), was formed to do ambient noise and marine mammal acoustic measurement and analysis. Three Environmental Acoustic Recording System (EARS) buoys, designed and produced by NAVOCEANO, were deployed by LADC in the northern Gulf of Mexico (GoM) in the summer of 2001. These bottom-moored omni-directional hydrophone recording systems were modified by NAVOCEANO to sample almost 12 kHz, so that the vocalizations of sperm whales could be recorded. The Sperm Whale Acoustic Monitoring Program (SWAMP) was conducted during that summer by the Minerals Management Service and its collaborators. The EARS buoys recorded during the entire 36 days of SWAMP from 17 July through 21 August of 2001. The EARS buoy hydrophones, 50m above the bottom, were placed on a downslope line, ending at the largest concentration of sperm whale sightings in the northern GoM, in 600m, 800m, and 1000m water depths. The moorings were instrumented with self-recording environmental sensors to obtain time series data of temperature, conductivity, and pressure at specified depths spanning the water column. Four cruises were made to deploy and recover the buoys and to collect a suite of environmental measurements, including CTD and XBT casts and a chirp sonar survey for bottom properties to support propagation modeling. In between the first and second cruises, Tropical Storm Barry moved through the area and changes in the oceanographic properties were observed. Each EARS buoy recorded a bandwidth of 5859 Hz for 36 days. These data clearly reveals sperm whale vocalizations, passing ships, and seismic airguns. Marine mammal vocalizations and airgun signatures have been isolated and are being analyzed. Spectral levels for ten minute averages of ambient noise on four different days show moderate shipping levels except during the passage of the tropical storm. A plateau in the noise spectrum from 200 to 1000Hz on one day is due to the presence of sperm whales. Spectrograms show sperm whale clicks and creaks and th- e seismic airgun signal is very clear.
    OCEANS '02 MTS/IEEE; 11/2002
  • A. Turgut, M. McCord, J. Newcomb, R. Fisher
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    ABSTRACT: Chirp sonar subbottom surveys have been conducted during a recent Littoral Acoustic Demonstration Center (LADC) experiment to invert bottom geoacoustic properties in the Northern Gulf of Mexico. Sediment properties such as density, porosity, and sound-speed profiles are inverted by using reflection amplitude and phase data obtained from a shallow-towed 2-12 kHz chirp sonar. High-quality subbottom images have been obtained with submeter resolution and up to 60 m penetration resolving several seafloor fault and diapir systems in the area. The attenuation coefficient is also estimated using the frequency shift method that seems to be relatively insensitive to reflection and transmission effects. The sound-speed and density structures of the LADC acoustic propagation tracks are efficiently mapped and made available for the numerical simulation studies of ambient noise and marine mammal acoustic propagation. The inversion results compare favorably with the previously reported sediment core data indicating that an accurate and rapid estimation of acoustical and physical properties of marine sediments is feasible.
    OCEANS '02 MTS/IEEE; 11/2002