Peter G. Cable's research while affiliated with Raytheon BBN Technologies and other places

Publications (31)

Article
Determinations of bottom scattering strength in the decade below 1 kHz under downward refracting conditions have been made using acoustic reverberation and transmission data from the 2001 East China Sea Asian Seas International Acoustic Experiment (ASIAEX). The measurements were performed using explosive sources and receiving hydrophones in ship-su...
Article
Full-text available
Low-frequency acoustic data acquired in the central East China Sea basin at two locations are analyzed for the purpose of making inferences on seabed acoustics. Previous geophysical studies indicate that the first sediment layer is composed of a fine to medium sand. The current analysis employs octave-averaged transmission loss (TL) versus range da...
Article
An analysis has been conducted of spatial and temporal variability of target echo-to-interference measurements made during Area Characterization Test III (ACT III) in 1995 in the Korea Strait. The measurements were made over a 5-day period for five fixed bistatic geometries (spatial scale of order 200 square km) using explosive sources, bottom-moun...
Article
Low-frequency monostatic reverberation data obtained during East China Sea ASIAEX in 2001 using Institute of Ocean Acoustics (Beijing) explosive sources and vertical line-receiving array on ShiYan-3 were analyzed in octave bands from 100-800 Hz to determine bottom-scattering strength dependence on bottom-scattering angle. Several methods for estima...
Article
Shallow?water (SW) coastal areas with depths between 40 and 200 m with bottom sediment layers (<25?m) formed by deposition and sea level variations are known to have frequency?dependent sound transmission and reverberation characteristics especially under the adverse conditions of downward refraction. Coastal ocean?dynamics complicates these enviro...
Article
A broadband model of seabed reverberation in a shallow water waveguide is used to analyze data measured in the Area Characterization Test I (ACT I). Given a source spectrum, a mean geoacoustic profile for the waveguide, and statistics characterizing the scattering sources (including fluctuations in seabed sound speed and density as well as seabed i...
Article
For various underwater acoustic applications such as beamforming and matched field processing, it is important to understand the spatial characteristics of shallow water acoustic fields. Oceanic and geoacoustic variabilities introduce random fluctuations into the fields, for which an important metric is the spatial coherence that is the correlation...
Article
Low-frequency monostatic reverberation data collected in the East China Sea on a VLA are analyzed to infer bottom scattering strength characteristics. The VLA was deployed and the data collected by researchers from the Institute of Ocean Acoustics, Beijing, China. Reverberation data originating from ranges from 3-15 km are analyzed using coherent a...
Article
Time series data collected on the APL-UW/URI VLA in the East China Sea as part of the Asian Sea International Acoustics Experiment are analyzed for the information they contain on the characteristics of the seabed. Sound generated by explosive sources deployed by the IOA propagates in a shallow water wave guide under downward refracting conditions,...
Article
Low frequency shallow water bottom scattering strength determinations conventionally involve accounting for the two-way transmission from source to scattering region to receiver and correcting for the size of the contributing bottom scattering area. Experiment uncertainties in transmission loss, bottom homogeneity and isotropy, contributions from v...
Article
Reverberant time series recorded in the East China Sea component of the Asian Seas International Acoustics Experiment are analyzed with the aid of a model of acoustic scattering from inhomogeneities in the seabed. Wideband sources deployed by the IOA were used to produce the time series, which were recorded on a thirty-two element VLA also deployed...
Article
The experiment, The Acoustic Characterization Test III, was conducted in the oceanographically complex Strait of Korea to accurately measure the sound transmission under known environmental conditions. Geoacoustic profiles derived from geophysical measurements, measured bathymetry, and sound-speed profiles were the basis for range dependent parabol...
Article
The experiment called the Acoustic Characterization Test III was performed in the oceanographically complex Strait of Korea. It was designed to provide accurate measurements of sound transmission and array signal gain under known environmental conditions. Bottom sampling and sub-bottom surveys coupled with archival geophysical information provided...
Article
The Acoustic Characterization Test III was performed in the oceanographically complex Strait of Korea to provide accurate measurements of sound transmission and coherence (array signal gain) under known environmental conditions. Bottom sampling and sub‐bottom surveys, coupled with archival geophysical information, provided the basis for geoacoustic...
Article
The effect of multipath induced time spread on the detectability of impulsive signals transmitted in shallow water is considered. The effective signal duration and temporal shape of received signal energy, two related features of the pulse spread associated with propagation, were analyzed for the shallow‐water coastal environments in the DARPA Area...
Technical Report
Full-text available
The study of reverberation is well known to be a very complex one with many competing mechanisms seen in real data (see Fig. 1). Much progress has been made in our understanding of reverberation (see for example ONR sponsored Acoustic Reverberation Special Research Program (ARSRP) and Critical Sea Test (CST) program publication lists and the abstra...
Article
The frequency dependence and level of shallow‐water (SW) reverberation, key parameters in sonar performance, represent the combined effect of scattering from the bottom, volume, and sea surface, and are a function of the transmission loss. SW, however, has the attribute of a seasonal dependence to the sound‐speed structure, which can emphasize one...
Article
Shallow?water transverse coherence lengths can be estimated by the measurement of the narrow?band coherence function, broadband correlation function, or the signal gain either from a direct measurement with a filled aperture or the steered beam response of a sparsely filled aperture. Signal?gain measurements with an array of sensors have a larger n...
Article
The Acoustic Characterization Test III (ACTIII) was conducted in the Strait of Korea in 1995. One of the goals of the experiment was to determine limitations on spatial signal processing due to environmental variabilities. Measurements of transmission loss and array signal gain (ASG) provide quantitative estimates of fluctuations in the acoustic fi...
Article
Recent experiments have measured the broadband sound transmission, coherency, reverberation and bottom backscattering strength in a variety of shallow?water environments with sand?silt bottoms. Ancillary range and time?dependent conductivity and temperature versus depth along with bathymetry were also obtained. The measurements were performed with...
Article
In this presentation, effects of small random fluctuations on the spatial coherence of the sound field in shallow water with multilayered sediments will be examined. These fluctuations occur within the water volume and the sediment layers as well as at the layer interfaces. Most previous work has dealt with either range‐independent or weakly range‐...
Conference Paper
For applications such as beamforming and matched field processing, it is important to understand spatial characteristics of shallow water acoustic fields. Oceanic and geoacoustic variabilities introduce random fluctuations into the fields, for which an important characteristic is the spatial coherence. The spatial coherence of the acoustic field is...
Article
Determinations of acoustic scattering strength for sand bottoms have been made at several different shallow-water areas under downward refracting sound propagation conditions in the frequency decade below 1 kHz. The measurements have been made using explosive sources detonated at mid-water depth and bottom-mounted vertical and horizontal hydrophone...
Article
For applications such as beamforming and matched field processing, the spatial behavior of the shallow water acoustic field is relevant. Oceanic and geoacoustic variabilities introduce random fluctuations into the field, which can be characterized by the spatial coherence. The spatial coherence of the acoustic field can be described by its correlat...
Article
Recent experiments performed in the shallow waters (100 m deep) of the Gulf of Mexico, East Continental Shelf of America, and the Korean Straits under the condition of downward refraction with sandy–silty clays are discussed. These experiments were performed with both explosive, air gun, and continuous sources covering the 100‐Hz to 1‐kHz frequency...
Article
Experimental measurements of signal coherence and array signal gain are reviewed for both deep and shallow water sound channels. The signal gain is related to single path or modal coherence lengths through well‐known relationships in the statistical theory of antennas. Signal gain measurements in the transverse and longitudinal directions are proff...
Article
The central questions in sonar system design concern the limits of coherent processing and are: What is the optimum frequency range and bandwidth?; How large of a receiving aperture is required?; What is the achievable detection range? These questions are determined by the propagation and scattering of sound. In the shallow water channel, under dow...
Article
Determinations of acoustic scattering strength for sand bottoms have been made at several shallow water sites under downward refracting sound propagation conditions in the frequency band 50 Hz to 1 kHz. The measurements have been made using explosive sources detonated at mid?water depth and received on two collocated, bottom?mounted hydrophone line...
Article
The shallow water channel is considered as a random, time?varying linear filter. The sources of temporal variation of channel properties considered are source and receiver motion and the motion of the surface (that is, windwaves and swell). Using an energy flux description for acoustic propagation, after Smith, Weston, and Brekhovskikh, and employi...
Article
The propagation and reverberation of sound in shallow water under downward refracting conditions is governed by the geoacoustic and scatteringproperties of the bottom. The active bistatic sonar equation for this case is developed and it is shown that, when the transmission to the target and the bottom are approximately the same for reverberation‐li...
Article
Acoustic transmission and reverberation measurements from 25 Hz to 1 kHz were made in 100 fathom water on the West Florida Shelf during Area Characterization Test I (ACT I) in September 1992. Explosive charges were detonated at 90?m depth and reverberation data were received on collocated vertical and horizontal hydrophone line arrays, each array h...

Citations

... We now investigate more precisely the depth and angle limits of the three regimes. First we define the water depth required to support a one-way ducted path (interacting with only one boundary) between a source or receiver and a target or scatterer at depths , (20) We also define the depths that bound paths that reflect at both boundaries (21) meaning respectively maximum and minimum depths between source and target positions remembering that the target is at the variable range . ...
... SW reverberation is often the most severe limiting factor in relation to the use of active sonar systems for target detection, localization and classification. Thus, SW reverberation has become a research area of intense interest [1]- [3]. ...
... where the proportionality coefficient, s bs0 , is the normal incidence (u h 08) backscattering cross-sectional area, and f is in Hertz. Within a frequency band of 10-900 kHz and for small (, 158) grazing angle (908-u) values, the frequency response parameter, C f , ranges circa 0-1.5 and is indicative of seabed type (Jia and Courtney, 2001;Greenlaw et al., 2004;Cable et al., 2006). Substituting Eq. ...
... A decoupling inversion method was employed by Knobles et al. 53,54 to estimate the surface sediment sound speed based on the ASIAEX time series data for 50-350 and 350-500 Hz bands. The inversion resulted in a sound speed of 1605-1621 m / s for a top sediment layer thickness of 6.7 m at the ASIAEX site. ...
... The slopes for the best case (upper dashed and dotted curve) and worst case (lower dotted curve) are 0.00647 and 0.18 dB/wavelength, respectively. The asterisk is the arraygain degradation estimated for the Straits of Korea by Carey et al. [9] for a similar acoustic wavelength and range. The averaged array-gain degradation observed in the South China Sea and the Carey measurement are comparable in magnitude. ...
... Therefore, the inversion methods based on acoustic field measurements (i.e., acoustic remote sensing) have been exploited to estimate low-frequency sediment properties. These inversion techniques involve normal mode analysis [10]- [25], matched field processing [26]- [28], signal waveform matching [29]- [32], transmission loss [33], [34], spatial coherence of reverberation and propagation [23], [35], ambient noise correlation [36], [37], reflection coefficient [38], [39], Hankel transform [40], [41], and multipath arrival time [42]. ...
... The second bottom scattering strength model uses a data derived and frequency dependent Lambert scattering strength, μ = μ d . 9 That frequency dependence is given by ...