Correlations and bicorrelations of a model 20 Hz finback whale signal and two actual data sinusoi... more Correlations and bicorrelations of a model 20 Hz finback whale signal and two actual data sinusoidal tran- sient signals are examined to investigate the suitability of correlation and bicorrelation processors for the detection of oscillatory transients. The connections to moments of the distribution of ordinate values of the signals and the signal bispectrum are also discussed. We show that the bicorrelation processor is not a particularly good detector compared to the correlation in the simplest detection scheme for the whale signal (and likely not for other signals of small third moment) and that the bispectrum of narrowband transients is generally small except for transients at very low frequency. If three or more sensors (or sets of sensors) receive a signal from a single source, the signal may be detected using the cross correlation of the sensors two at a time or by using a correlation of three at one time. If a known transient is sought, it may be cross correlated with the signal at a single sensor (matched filtering) or it may be simultaneously correlated with the signal at two sensors. These approaches are the main concern of this paper. The research can be extended to correlations of four or more signals simultaneously, to localization in time or space, and to source identification. In this work we consider only source detection and examine mainly the question of correlations three at a time versus those taken two at a time. We concentrate on some oscillatory signals which are of a type generated by vibratory sources. We do not include the complications of multipath arrivals and coherence loss. Initially we discuss the problems of correlation processing for underwater acoustic transients and the role of the autocorrelation in the analysis. We give sample transients and their properties. Definitions are set forth for ordinary and higher order correlations, and their spectra are related to the spectra of the transients. The importance of moments of ordinate values of the transients is stressed and a histogram of ordinate values is analyzed. The principal domains of bispec- tra for narrow and medium band transients and low frequency transients are discussed. Initial performance analyses of corre- lation and bicorrelation detectors are given.
[1993 Proceedings] IEEE Signal Processing Workshop on Higher-Order Statistics
ABSTRACT Prefiltering, or limiting the spectral domain of data, improves maximum magnitude correl... more ABSTRACT Prefiltering, or limiting the spectral domain of data, improves maximum magnitude correlation peak detectors, both ordinary and higher order, for known and unknown sources. The only exception is the matched filter, which intrinsically contains prefiltering. For the cases studied, prefiltering generally has a higher order advantage, i.e., for higher order and in higher dimensions, it is even more effective than in one dimension for the ordinary correlation. Geometrical considerations can give some insight into this advantage. The tricorrelation detector with prefiltering performs best for all eight tested signals in the unknown source tests, and is the best detector for seven of the eight signals in the known source tests. Prefiltering for higher order correlation detectors involves only one-dimensional filtering and so is computationally efficient.
The Journal of the Acoustical Society of America, 2007
The Littoral Acoustic Demonstration Center conducted a passive acoustic experiment in the Norther... more The Littoral Acoustic Demonstration Center conducted a passive acoustic experiment in the Northern Gulf of Mexico, about 120 nmi south of the Mississippi delta between July 5 and July 17, 2007. The primary objective of the experiment was to make probably the first passive acoustic recordings of beaked whales in the Gulf of Mexico. Six environmental acoustic recording system (EARS) buoys were deployed in two triangular configurations in about 1,500 m water with the hydrophones located at a 1,000 m depth. The distance between the two triangles was about 20 nmi. Each EARS buoy recorded in the frequency band of 100 Hz–96 kHz for ten consecutive days, with a total data amount collected of about 3 Tbytes. More than ten different marine mammal species were identified in the vicinity of the buoys during visual observations, which supported the experiment including three different types of beaked whales. Preliminary environmental and acoustic data analysis, including average noise curves and different species iden...
The Journal of the Acoustical Society of America, 2002
Three bottom-moored hydrophones, 50 m above the bottom, were placed on a downslope line, ending a... more Three bottom-moored hydrophones, 50 m above the bottom, were placed on a downslope line, ending at the largest concentration of sperm whale sightings in the northern Gulf of Mexico, in 600 m, 800 m, and 1000 m water depths. These depths were chosen after upslope propagation modeling, using historical databases, showed transmission losses greater than 110 dB at hydrophones near
The Journal of the Acoustical Society of America, 1994
Prefiltering, or limiting the passband of a received signal, can be used to improve ordinary corr... more Prefiltering, or limiting the passband of a received signal, can be used to improve ordinary correlation threshold detector performance for an unknown source model. For the known source model, the cross‐correlation detector is equivalent to matched filtering, and intrinsically contains prefiltering. Prefiltering also improves higher‐order correlation threshold detector performance, but often with more advantage than seen in the ordinary correlation detector. This is true for both the unknown and known source models. Geometric interpretations are given to provide insight into the origin of potential higher‐order advantage. Eight energy signals, each with three different Fourier magnitude‐based filters, are used to test the cross‐correlation, bicorrelation, and tricorrelation detectors by Monte Carlo simulation and hypothesis testing. Significant signal‐to‐noise ratio (SNR) gains are evident for both the known and unknown source models with the tricorrelation exhibiting the largest gains. The tricorrelation...
IEEE Workshop on Statistical Signal and Array Processing, 1996
The passive sonar classification problem can be decomposed into two stages: (l) recovering the so... more The passive sonar classification problem can be decomposed into two stages: (l) recovering the source time signature of a transient event from a set of received signals by accounting for environmental distortion effects, and (2) applying a pattern recognition algorithm to the estimated source signature for final classification. The minimum entropy method is studied with regard to its performance in
... [IO] ' Aaron Thode, David K. Mellinger, Sarah Stienessen, Anthony Martinez, and Keith Mu... more ... [IO] ' Aaron Thode, David K. Mellinger, Sarah Stienessen, Anthony Martinez, and Keith Mullin, Depth-dependent acoustic. features of diving sperm whales (Physeter macrocephalus) in the Gulf of Mexico, J. Acoust. Soc. Am., vol. 112, pp. 308-321,2002, [I I] Jod Newcomb, ...
The Journal of the Acoustical Society of America, 2002
ABSTRACT From September 26 through November 2, 2000 the U.S. and Japan conducted a joint experime... more ABSTRACT From September 26 through November 2, 2000 the U.S. and Japan conducted a joint experiment in the New Jersey Bight off the U.S. East Coast. The experiment was conducted in three legs, the first of which investigated low frequency acoustic fluctuations in the presence of a shelf/slope front and internal waves. Legs II and III investigated acoustic scattering at 5.5 kHz and methods of acoustic inversion for sea floor properties, respectively. In this paper we will focus on the experimental results of leg I and discuss implications for doing acoustic inversions in a strongly fluctuating medium. Theoretical results based on the Pekeris waveguide show that a large‐scale, slowly fluctuating sound speed can cause rapid fluctuations in the acoustic field in the form of acoustic harmonics. Pekeris waveguide calculations are compared with a subset of the acoustic data. Theoretical results and parabolic equation simulations are used to show the impact of the water column sound speed on the horizontal wavenumbers and hence on acoustic inversion methods that utilize them. [Work supported by ONR, Program Element PE62435N.]
The Journal of the Acoustical Society of America, 2001
Accurate prediction of the effects of a shallow‐water propagation channel on acoustic signal dist... more Accurate prediction of the effects of a shallow‐water propagation channel on acoustic signal distortion would aid in the optimal design of shallow‐water communication systems. It has been shown that the correlation between modeled (based on a parabolic equation approach) and measured ocean responses decreases significantly with increasing propagation range because of the mismatch in relative amplitudes and time delays between the modeled and measured bottom‐interacting arrivals. This raises the question whether the discrepancies are related to the particular modeling algorithm or to insufficient information about the propagation channel. A new normal mode range‐dependent algorithm is used to simulate the acoustic response for the source–receiver configuration used in an experiment in the Atlantic Ocean at the Southern end of the Blake Plateau in which a 25–150 Hz linear, frequency‐modulated source signal is received on a 15‐element vertical array. The normalized correlation coefficients between source and...
Correlations and bicorrelations of a model 20 Hz finback whale signal and two actual data sinusoi... more Correlations and bicorrelations of a model 20 Hz finback whale signal and two actual data sinusoidal tran- sient signals are examined to investigate the suitability of correlation and bicorrelation processors for the detection of oscillatory transients. The connections to moments of the distribution of ordinate values of the signals and the signal bispectrum are also discussed. We show that the bicorrelation processor is not a particularly good detector compared to the correlation in the simplest detection scheme for the whale signal (and likely not for other signals of small third moment) and that the bispectrum of narrowband transients is generally small except for transients at very low frequency. If three or more sensors (or sets of sensors) receive a signal from a single source, the signal may be detected using the cross correlation of the sensors two at a time or by using a correlation of three at one time. If a known transient is sought, it may be cross correlated with the signal at a single sensor (matched filtering) or it may be simultaneously correlated with the signal at two sensors. These approaches are the main concern of this paper. The research can be extended to correlations of four or more signals simultaneously, to localization in time or space, and to source identification. In this work we consider only source detection and examine mainly the question of correlations three at a time versus those taken two at a time. We concentrate on some oscillatory signals which are of a type generated by vibratory sources. We do not include the complications of multipath arrivals and coherence loss. Initially we discuss the problems of correlation processing for underwater acoustic transients and the role of the autocorrelation in the analysis. We give sample transients and their properties. Definitions are set forth for ordinary and higher order correlations, and their spectra are related to the spectra of the transients. The importance of moments of ordinate values of the transients is stressed and a histogram of ordinate values is analyzed. The principal domains of bispec- tra for narrow and medium band transients and low frequency transients are discussed. Initial performance analyses of corre- lation and bicorrelation detectors are given.
[1993 Proceedings] IEEE Signal Processing Workshop on Higher-Order Statistics
ABSTRACT Prefiltering, or limiting the spectral domain of data, improves maximum magnitude correl... more ABSTRACT Prefiltering, or limiting the spectral domain of data, improves maximum magnitude correlation peak detectors, both ordinary and higher order, for known and unknown sources. The only exception is the matched filter, which intrinsically contains prefiltering. For the cases studied, prefiltering generally has a higher order advantage, i.e., for higher order and in higher dimensions, it is even more effective than in one dimension for the ordinary correlation. Geometrical considerations can give some insight into this advantage. The tricorrelation detector with prefiltering performs best for all eight tested signals in the unknown source tests, and is the best detector for seven of the eight signals in the known source tests. Prefiltering for higher order correlation detectors involves only one-dimensional filtering and so is computationally efficient.
The Journal of the Acoustical Society of America, 2007
The Littoral Acoustic Demonstration Center conducted a passive acoustic experiment in the Norther... more The Littoral Acoustic Demonstration Center conducted a passive acoustic experiment in the Northern Gulf of Mexico, about 120 nmi south of the Mississippi delta between July 5 and July 17, 2007. The primary objective of the experiment was to make probably the first passive acoustic recordings of beaked whales in the Gulf of Mexico. Six environmental acoustic recording system (EARS) buoys were deployed in two triangular configurations in about 1,500 m water with the hydrophones located at a 1,000 m depth. The distance between the two triangles was about 20 nmi. Each EARS buoy recorded in the frequency band of 100 Hz–96 kHz for ten consecutive days, with a total data amount collected of about 3 Tbytes. More than ten different marine mammal species were identified in the vicinity of the buoys during visual observations, which supported the experiment including three different types of beaked whales. Preliminary environmental and acoustic data analysis, including average noise curves and different species iden...
The Journal of the Acoustical Society of America, 2002
Three bottom-moored hydrophones, 50 m above the bottom, were placed on a downslope line, ending a... more Three bottom-moored hydrophones, 50 m above the bottom, were placed on a downslope line, ending at the largest concentration of sperm whale sightings in the northern Gulf of Mexico, in 600 m, 800 m, and 1000 m water depths. These depths were chosen after upslope propagation modeling, using historical databases, showed transmission losses greater than 110 dB at hydrophones near
The Journal of the Acoustical Society of America, 1994
Prefiltering, or limiting the passband of a received signal, can be used to improve ordinary corr... more Prefiltering, or limiting the passband of a received signal, can be used to improve ordinary correlation threshold detector performance for an unknown source model. For the known source model, the cross‐correlation detector is equivalent to matched filtering, and intrinsically contains prefiltering. Prefiltering also improves higher‐order correlation threshold detector performance, but often with more advantage than seen in the ordinary correlation detector. This is true for both the unknown and known source models. Geometric interpretations are given to provide insight into the origin of potential higher‐order advantage. Eight energy signals, each with three different Fourier magnitude‐based filters, are used to test the cross‐correlation, bicorrelation, and tricorrelation detectors by Monte Carlo simulation and hypothesis testing. Significant signal‐to‐noise ratio (SNR) gains are evident for both the known and unknown source models with the tricorrelation exhibiting the largest gains. The tricorrelation...
IEEE Workshop on Statistical Signal and Array Processing, 1996
The passive sonar classification problem can be decomposed into two stages: (l) recovering the so... more The passive sonar classification problem can be decomposed into two stages: (l) recovering the source time signature of a transient event from a set of received signals by accounting for environmental distortion effects, and (2) applying a pattern recognition algorithm to the estimated source signature for final classification. The minimum entropy method is studied with regard to its performance in
... [IO] ' Aaron Thode, David K. Mellinger, Sarah Stienessen, Anthony Martinez, and Keith Mu... more ... [IO] ' Aaron Thode, David K. Mellinger, Sarah Stienessen, Anthony Martinez, and Keith Mullin, Depth-dependent acoustic. features of diving sperm whales (Physeter macrocephalus) in the Gulf of Mexico, J. Acoust. Soc. Am., vol. 112, pp. 308-321,2002, [I I] Jod Newcomb, ...
The Journal of the Acoustical Society of America, 2002
ABSTRACT From September 26 through November 2, 2000 the U.S. and Japan conducted a joint experime... more ABSTRACT From September 26 through November 2, 2000 the U.S. and Japan conducted a joint experiment in the New Jersey Bight off the U.S. East Coast. The experiment was conducted in three legs, the first of which investigated low frequency acoustic fluctuations in the presence of a shelf/slope front and internal waves. Legs II and III investigated acoustic scattering at 5.5 kHz and methods of acoustic inversion for sea floor properties, respectively. In this paper we will focus on the experimental results of leg I and discuss implications for doing acoustic inversions in a strongly fluctuating medium. Theoretical results based on the Pekeris waveguide show that a large‐scale, slowly fluctuating sound speed can cause rapid fluctuations in the acoustic field in the form of acoustic harmonics. Pekeris waveguide calculations are compared with a subset of the acoustic data. Theoretical results and parabolic equation simulations are used to show the impact of the water column sound speed on the horizontal wavenumbers and hence on acoustic inversion methods that utilize them. [Work supported by ONR, Program Element PE62435N.]
The Journal of the Acoustical Society of America, 2001
Accurate prediction of the effects of a shallow‐water propagation channel on acoustic signal dist... more Accurate prediction of the effects of a shallow‐water propagation channel on acoustic signal distortion would aid in the optimal design of shallow‐water communication systems. It has been shown that the correlation between modeled (based on a parabolic equation approach) and measured ocean responses decreases significantly with increasing propagation range because of the mismatch in relative amplitudes and time delays between the modeled and measured bottom‐interacting arrivals. This raises the question whether the discrepancies are related to the particular modeling algorithm or to insufficient information about the propagation channel. A new normal mode range‐dependent algorithm is used to simulate the acoustic response for the source–receiver configuration used in an experiment in the Atlantic Ocean at the Southern end of the Blake Plateau in which a 25–150 Hz linear, frequency‐modulated source signal is received on a 15‐element vertical array. The normalized correlation coefficients between source and...
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Papers by Robert Field