Arslan M. Tashmukhambetov

Three-dimensional seismic array characterization study: experiment and modeling.

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 Greens 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.

Modeling the three‐dimensional field of a seismic airgun array and comparison to 2003 measured data.

The full three‐dimensional field of a seismic airgun array is modeled using an enhanced parabolic equation run on a parallel cluster computer system, which is part of the Louisiana Optical Network Initiative network cluster. Source signatures are calculated using GUNDALF and NUCLEUS softwares. The calculated results are compared to available measurements collected in Green Canyon in the northern Gulf of Mexico in 2003. Three‐dimensional maps showing angular variation (both emission and azimuthal angles) and range dependence are generated, which show peak pressures, sound exposure levels, total shot energy spectra, and one‐third octave band analyses. [Research supported by the International Association of Oil and Gas Producers and the International Association of Geophysical Contractors.]

Acoustic identification of beaked and sperm whales

Identification of individual marine mammals acoustically was initially motivated in this research by spectrograms of the littoral acoustic demonstration center Northern Gulf of Mexico data containing sperm whale click codas, which showed that clicks in a coda have a spectral pattern that persists across all the clicks in that coda. The hypothesis is that each coda originates from a single whale, and all codas with similar properties come from the same whale. Self‐organizing maps (SOMs) are used to compare and classify the time series, Fourier transforms, and wavelet transforms of each coda in order to determine how many whales are present. The results show that SOMs have promise for classifying underwater acoustic coda signals from sperm whales. A similarity measure has been applied to both coda and echolocation clicks and has shown some success in associating both types of clicks with individuals. Other forms of cluster analysis are also considered. Progress in the classification of sperm whale clicks has motivated the application of similar analysis to beaked whale echolocation clicks. Time‐frequency plots show interesting details. Preliminary results for beaked whale click analysis are presented. [Research supported by ONR.]

Localization to verify the identification of individual sperm whales using click properties.

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 class...

Source characterization study 2007: The three‐dimensional primary field of a seismic airgun array.

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 source characterization study 2007: A detailed three dimensional acoustic field measurement of a seismic airgun array.

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.]

Use of high performance computing resources for underwater acoustic modeling.

The majority of standard underwater propagation models provide a two‐dimensional (range and depth) acoustic field for a single frequency point source. Computational resource demand increases considerably when the three‐dimensional acoustic field of a broad‐band spatially extended source is of interest. An upgrade of the standard parabolic equation model RAM for use in a high‐performance computing (HPC) environment is discussed. A benchmarked upgraded version of RAM is used in the Louisiana Optical Network Initiative HPC‐environment to model the three‐dimensional acoustic field of a seismic airgun array. Four‐dimensional visualization (time and space) of the generated data volume is also addressed. [Research supported by the Louisiana Optical Network Initiative, TeraGrid Fellowship, and the Joint Industry Programme through the International Association of Oil and Gas Producers.]

Environmental acoustic recording system (EARS) buoys for marine animal acoustics.

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 recordi...

Using parallel programming and a three‐dimensional visualization cave to map the acoustic energy distribution from a seismic array in the ocean

Modeling and visualization of the dynamic acoustic field during a seismic exploration survey represent a computational challenge due to broadband, directional nature of the acoustic signal radiated by a seismic array. Standard acoustic propagation models (RAM and SWAMP) are upgraded for parallel processing and tested in the LONI (the Louisiana Optical Network Initiative) environment, using the Louisiana fiber optics grid computing network to model the three‐dimensional time‐varying acoustic field in the ocean during a seismic exploration survey. The generated volume of data is transferred and visualized in the advanced immersive visualization environment, supported by Louisiana Immersive Technology Enterprise (LITE) facilities. The proposed technology is one of the first steps in developing real‐time monitoring of the acoustic energy distribution in a large oceanic volume. This can be beneficial for environmental impact assessment and regulation and for seismic survey design. [Research supported in part b...

Identifying individual clicking whales acoustically amid the clutter of other clicking whales.

Exceptionally clear recordings of sperm whale (Physeter macrocephalus) codas reveal time and frequency properties, which show that clicks within a coda are remarkably similar to each other but that they can differ from clicks in other codas. This is consistent with the hypothesis that individual whales can be identified by the characteristics within their codas. Research has centered on the cluster analysis of these codas to help establish whether acoustic identification of individuals is possible. Recently the cluster analysis has been made more robust. This increases the confidence in the applicability of the approach. Data are now available to couple visual sightings and acoustic tracking with recordings for acoustic identification to give an independent verification of the analysis. Acoustic identification of individuals has also been attempted using isolated echolocation clicks of sperm and beaked whales (Mesoplodon densirostris and Ziphius cavirostris). Although this is a more difficult and problematic undertaking, there has been some promising cluster analysis. Again data for acoustic tracking and visual observations are now available with the recordings for acoustic identification using echolocation clicks to test and perhaps validate the method. [Research supported in part by SPAWAR.]