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David R Dowling - One of the best experts on this subject based on the ideXlab platform.

  • measurements of the correlation of the Frequency Difference autoproduct with acoustic and predicted autoproduct fields in the deep ocean
    Journal of the Acoustical Society of America, 2021
    Co-Authors: David J Geroski, Matthew A Dzieciuch, David R Dowling
    Abstract:

    Frequency-domain spatial-correlation analysis of recorded acoustic fields is typically limited to the bandwidth of the recordings. A previous study [Lipa, Worthmann, and Dowling (2018) J. Acoust. Soc. Am. 143(4), 2419–2427] suggests that limiting such analysis to in-band frequencies is not strictly necessary in a Lloyd's mirror environment. In particular, below-band field information can be retrieved from the Frequency-Difference autoproduct, a quadratic product of measured complex pressure-field amplitudes from two nearby frequencies. The Frequency-Difference autoproduct is a surrogate field that mimics a genuine acoustic field at the Difference Frequency. Here, spatial-correlation analysis is extended to deep-ocean acoustic fields measured during the PhilSea10 experiment. The Frequency-Difference autoproduct, at Difference frequencies from 0.0625 to 15 Hz, is determined from hundreds of Philippine Sea recordings of 60 or 100 Hz bandwidth signals with center frequencies from 172.5 to 275 Hz broadcast to a vertical receiving array 129–450 km away. The measured autoproducts are cross correlated along the array with predicted acoustic fields and with predicted autoproduct fields at corresponding below-band frequencies. Stable measured cross correlations as high as 80%–90% are found at the low end of the investigated Difference-Frequency range, with consistent correlation loss due to mismatch at the higher below-band frequencies.

  • long range Frequency Difference source localization in the philippine sea
    Journal of the Acoustical Society of America, 2019
    Co-Authors: David J Geroski, David R Dowling
    Abstract:

    Matched field processing (MFP) refers to a variety of source localization schemes for known complicated environments and involves matching measured and calculated (replica) fields to identify source locations. MFP may fail for several reasons, most notably when the calculated fields are insufficiently accurate. This error commonly prevents MFP-based long-range (>100 km) source localization in the deep ocean (from 5 to 6 km depth) for signal frequencies of hundreds of Hz, even when extensive high-signal-to-noise ratio field measurements are available. Recently, below-band MFP utilizing the Frequency-Difference autoproduct [Worthmann, Song, and Dowling (2015). J. Acoust. Soc. Am, 138(6), 3549–3562] achieved some shallow-ocean localization success at a 3 km source-to-array range with signal frequencies in the tens of kHz. The performance of this technique, when extended to matching the measured Frequency-Difference autoproduct with a composite mode-ray replica, is described here for deep ocean source localization. The ocean propagation data come from the PhilSea10 experiment and involve source-to-array ranges from 129 to 379 km and nominal 100-Hz-bandwidth signals having center frequencies from 250 to 275 Hz. Based on an incoherent average of five signal samples, the Frequency-Difference technique was 90%–100% successful at four different source-to-array ranges using single-digit-Hz Difference frequencies.Matched field processing (MFP) refers to a variety of source localization schemes for known complicated environments and involves matching measured and calculated (replica) fields to identify source locations. MFP may fail for several reasons, most notably when the calculated fields are insufficiently accurate. This error commonly prevents MFP-based long-range (>100 km) source localization in the deep ocean (from 5 to 6 km depth) for signal frequencies of hundreds of Hz, even when extensive high-signal-to-noise ratio field measurements are available. Recently, below-band MFP utilizing the Frequency-Difference autoproduct [Worthmann, Song, and Dowling (2015). J. Acoust. Soc. Am, 138(6), 3549–3562] achieved some shallow-ocean localization success at a 3 km source-to-array range with signal frequencies in the tens of kHz. The performance of this technique, when extended to matching the measured Frequency-Difference autoproduct with a composite mode-ray replica, is described here for deep ocean source localiz...

  • use of Frequency Difference beamforming for scatterer localization
    Journal of the Acoustical Society of America, 2019
    Co-Authors: Alexander S Douglass, Kely J Markley, David R Dowling
    Abstract:

    Acoustic fields interacting with discontinuities or environmental variations lead to secondary scattered fields superimposed onto incident fields. As a result, the signal measured at a remote receiving array will be modified by the scatterer’s presence. Prior work has shown that the effects of strong random scattering are reduced using Frequency-Difference beamforming to downshift the analysis to a below-band Frequency known to be less impacted by scattering. In some applications, information about a scatterer is desired, such as location, shape, or composition. However, a relatively weak scattered field from a single scatterer is difficult to detect when the incident field dominates the measurements, as both conventional and Frequency-Difference beamforming ambiguity surfaces primarily provide the incident field’s source information. Here, a subtraction-based algorithm is implemented with Frequency-Difference beamforming to locate the position of a single scatterer near a source. Simulations and water tank experiments with a 110 kHz center Frequency signal are considered for incident and scattered fields with a 4 cm diameter spherical scatterer, where the scattered field’s received energy is roughly 2% that of the incident field. The ability to downshift the Frequency demonstrates a more robust implementation of subtraction-based algorithms for locating weak scatterers without prior location knowledge. [Work supported by ONR.]

  • explorations of in situ source localization in the deep ocean using Frequency Difference matched field processing and matched autoproduct processing
    Journal of the Acoustical Society of America, 2018
    Co-Authors: David J Geroski, David R Dowling
    Abstract:

    Matched field processing (MFP) is a well-known technique for source localization in challenging environments. MFP involves correlating array-recorded fields with calculated replica fields developed from knowledge of the acoustic environment. Incomplete knowledge of the environment causes mismatch between measured and calculated fields, and this mismatch can cause MFP to fail at relevant ranges and frequencies in the deep ocean. Given that the severity of this mismatch increases with Frequency, a proposed remedy to the mismatch problem is to analyze the Frequency-Difference autoproduct of the recorded field, rather than the field itself. The phase of the Frequency-Difference autoproduct is expected to mimic that of an out-of-band field at a selectable below-band Frequency, thereby mitigating the severity of the mismatch at in-band frequencies. This autoproduct is then matched either to a replica field at the below-band Frequency, or to an appropriate calculated autoproduct field. This presentation explores these methods, and higher-order corrections, to localize moored sources using data from the North Pacific Acoustic Library. Localization statistics are presented based on the closest moored source, 130 km from the receiving array with a signal bandwidth from 200 to 300 Hz. [Sponsored by ONR.]

  • cross term analysis in Frequency Difference based source localization methods
    Journal of the Acoustical Society of America, 2018
    Co-Authors: Brian M Worthmann, David R Dowling
    Abstract:

    In previous work, it has been shown that a quadratic product of Frequency-domain acoustic fields at different frequencies but the same spatial location leads to an auxiliary field which may contain field information at frequencies below the original signal’s bandwidth (Worthmann, Song and Dowling, 2015, JASA 138, 3549-3562). This quadratic product, termed the Frequency-Difference autoproduct, has been shown to be valuable for beamforming and source localization in the presence of environmental mismatch and/or array sparseness. However, in a multipath environment, this quadratic product leads to undesired cross-terms. Bandwidth averaging procedures have been found to suppress some of their detrimental influences in some cases, but not all. Additionally, the poor dynamic range observed in Frequency-Difference beamforming and Frequency-Difference matched field processing are associated with the imperfect mitigation of these cross-terms. In this presentation, the nature of these cross-terms is analyzed, and signal processing tools are developed which attempt to robustly mitigate the detrimental effects of these cross terms. These signal processing tools can be used to potentially improve localization performance when using Frequency-Difference autoproduct-based source localization schemes. [Sponsored by ONR and NSF]

Andrew J Oxenham - One of the best experts on this subject based on the ideXlab platform.

  • Frequency Difference limens as a function of fundamental Frequency and harmonic number
    The Journal of the Acoustical Society of America, 2018
    Co-Authors: Anahita H. Mehta, Andrew J Oxenham
    Abstract:

    Several studies have investigated the relation between the lowest harmonic present in a complex tone and fundamental Frequency (F0) Difference limens (F0DLs). It is generally assumed that F0DLs are smaller when lower harmonics are present and that the ability to discriminate small changes in F0 worsen as harmonic number increases. This worsening of performance has been attributed to a lack of peripherally resolved harmonics. This assumption was tested by measuring F0DLs for harmonic complexes where the lowest harmonic present in a twelve-harmonic complex tone varied from the 3rd to the 15th harmonic, with F0s varying from 30 Hz to 2000 Hz. The harmonics were presented in either sine or random phase and were embedded in threshold-equalizing noise. Aside from F0s between 100 and 400 Hz, performance did not follow the expected pattern of good performance with low-numbered (resolved) harmonics and poorer performance with high-numbered (unresolved) harmonics. At lower F0s, performance was relatively constant a...

  • characterizing the dependence of pure tone Frequency Difference limens on Frequency duration and level
    Hearing Research, 2012
    Co-Authors: Christophe Micheyl, Li Xiao, Andrew J Oxenham
    Abstract:

    This study examined the relationship between the Difference limen for Frequency (DLF) of pure tones and three commonly explored stimulus parameters of Frequency, duration, and sensation level. Data from 12 published studies of pure-tone Frequency discrimination (a total of 583 DLF measurements across 77 normal-hearing listeners) were analyzed using hierarchical (or “mixed-effects”) generalized linear models. Model parameters were estimated using two approaches (Bayesian and maximum likelihood). A model in which log-transformed DLFs were predicted using a sum of power-law functions plus a random subject- or group-specific term was found to explain a substantial proportion of the variability in the psychophysical data. The results confirmed earlier findings of an inverse-square-root relationship between log-transformed DLFs and duration, and of an inverse relationship between log(DLF) and sensation level. However, they did not confirm earlier suggestions that log(DLF) increases approximately linearly with the square-root of Frequency; instead, the relationship between Frequency and log(DLF) was best fitted using a power function of Frequency with an exponent of about 0.8. These results, and the comprehensive quantitative analysis of pure-tone Frequency discrimination on which they are based, provide a new reference for the quantitative evaluation of models of Frequency (or pitch) discrimination.

  • further evidence that fundamental Frequency Difference limens measure pitch discrimination
    Journal of the Acoustical Society of America, 2012
    Co-Authors: Christophe Micheyl, Claire Ryan, Andrew J Oxenham
    Abstract:

    Difference limens for complex tones (DLCs) that differ in F0 are widely regarded as a measure of periodicity-pitch discrimination. However, because F0 changes are inevitably accompanied by changes in the frequencies of the harmonics, DLCs may actually reflect the discriminability of individual components. To test this hypothesis, DLCs were measured for complex tones, the component frequencies of which were shifted coherently upward or downward by ΔF = 0%, 25%, 37.5%, or 50% of the F0, yielding fully harmonic (ΔF = 0%), strongly inharmonic (ΔF = 25%, 37.5%), or odd-harmonic (ΔF = 50%) tones. If DLCs truly reflect periodicity-pitch discriminability, they should be larger (worse) for inharmonic tones than for harmonic and odd harmonic tones because inharmonic tones have a weaker pitch. Consistent with this prediction, the results of two experiments showed a non-monotonic dependence of DLCs on ΔF, with larger DLCs for ΔF’s of ±25% or ±37.5% than for ΔF’s of 0 or ±50% of F0. These findings are consistent with ...

  • further evidence that fundamental Frequency Difference limens measure pitch discrimination
    Journal of the Acoustical Society of America, 2012
    Co-Authors: Christophe Micheyl, Claire Ryan, Andrew J Oxenham
    Abstract:

    Difference limens for complex tones (DLCs) that differ in F0 are widely regarded as a measure of periodicity-pitch discrimination. However, because F0 changes are inevitably accompanied by changes in the frequencies of the harmonics, DLCs may actually reflect the discriminability of individual components. To test this hypothesis, DLCs were measured for complex tones, the component frequencies of which were shifted coherently upward or downward by ΔF = 0%, 25%, 37.5%, or 50% of the F0, yielding fully harmonic (ΔF = 0%), strongly inharmonic (ΔF = 25%, 37.5%), or odd-harmonic (ΔF = 50%) tones. If DLCs truly reflect periodicity-pitch discriminability, they should be larger (worse) for inharmonic tones than for harmonic and odd harmonic tones because inharmonic tones have a weaker pitch. Consistent with this prediction, the results of two experiments showed a non-monotonic dependence of DLCs on ΔF, with larger DLCs for ΔF’s of ±25% or ±37.5% than for ΔF’s of 0 or ±50% of F0. These findings are consistent with models of pitch perception that involve harmonic templates or with an autocorrelation-based model provided that more than just the highest peak in the summary autocorrelogram is taken into account.

Qin Gong - One of the best experts on this subject based on the ideXlab platform.

  • Correlation between the Frequency Difference limen and an index based on principal component analysis of the Frequency-following response of normal hearing listeners.
    Hearing research, 2016
    Co-Authors: Xiaochen Zhang, Qin Gong
    Abstract:

    Subcortical phase locking tends to reflect performance Differences in tasks related to pitch perception across different types of populations. Enhancement or attenuation in its strength may correspond to population excellence or deficiency in pitch perception. However, it is still unclear whether Differences in perceptual capability among individuals with normal hearing can be predicted by subcortical phase locking. In this study, we examined the brain-behavior relationship between Frequency-following responses (FFRs) evoked by pure/sweeping tones and Frequency Difference limens (FDLs). FFRs are considered to reflect subcortical phase locking, and FDLs are a psychophysical measure of behavioral performance in pitch discrimination. Traditional measures of FFR strength were found to be poorly correlated with FDL. Here, we introduced principal component analysis into FFR analysis and extracted an FFR component that was correlated with individual pitch discrimination. The absolute value of the score of this FFR principal component (but not the original score) was negatively correlated with FDL, regardless of stimulus type. The topographic distribution of this component was relatively constant across individuals and across stimulus types, and the inferior colliculus was identified as its origin. The findings suggest that subcortical phase locking at certain but not all FFR generators carries the neural information required for the prediction of individual pitch perception among humans with normal hearing.

  • Frequency Difference beyond behavioral limen reflected by Frequency following response of human auditory brainstem
    Biomedical Engineering Online, 2014
    Co-Authors: Qin Gong
    Abstract:

    Background The present study investigated whether the Frequency-following response (FFR) of the auditory brainstem can represent individual Frequency-discrimination ability.

  • Frequency Difference beyond behavioral limen reflected by Frequency following response of human auditory brainstem
    Biomedical Engineering Online, 2014
    Co-Authors: Qin Gong
    Abstract:

    Background: The present study investigated whether the Frequency-following response (FFR) of the auditory brainstem can represent individual Frequency-discrimination ability. Method: We measured behavioral Frequency-Difference limens (FDLs) in normal hearing young adults. Then FFRs were evoked by two pure tones, whose Frequency Difference was no larger than behavioral FDL. Discrimination of FFRs to individual frequencies was conducted as the neural representation of stimulus Frequency Difference. Participants were 15 Chinese college students (ages 19–25; 3 males, 12 females) with normal hearing characteristics. Results: According to discriminative neural representations of individual frequencies, FFRs accurately reflected individual FDLs and detected stimulus-Frequency Differences smaller than behavioral threshold (e.g., 75% of FDL). Conclusions: These results suggest that when a Frequency Difference cannot be behaviorally distinguished, there is still a possibility of it being detected physiologically.

  • pitch perception assessed by Frequency Difference limen and Frequency following response
    2013
    Co-Authors: Qin Gong, Wensheng Sun
    Abstract:

    The improvement of pitch perception is a hot spot in cochlear implant algorithm research. In order to provide objective and effective guidance for the algorithm research, psychoacoustic method and brainstem Frequency following response (FFR) were studied in this paper to assess the ability of pitch perception among young people who exhibited the same normal hearing sensitivity. Eleven Chinese college students participated in both the psychoacoustic experiment and FFR experiment. Using pure tone as the stimulus, psychoacoustic Frequency Difference limen (FDL) and FFR neural pitch strength were measured. Both of them were used as parameters for evaluating pitch perception ability. FFR pitch strengths were extracted by three different methods which were autocorrelation, chirp z-transform and spectrogram. FFR pitch strengths correlated to a certain extent with FDL results and the FFR pitch strength by autocorrelation showed the highest degree of correlation. The results imply that in the same normal hearing population, features extracted from FFR signal can represent pitch perception ability of subjects. FFR features can be expected to become objective and effective parameters for assessing cochlear implant algorithms.

Christophe Micheyl - One of the best experts on this subject based on the ideXlab platform.

  • Supplemental Data Perceptual Organization of Sound Begins in the Auditory Periphery
    2015
    Co-Authors: Daniel Pressnitzer, Christophe Micheyl, Mark Sayles, Ian M. Winter
    Abstract:

    Stimuli. The stimuli were sequences of pure tones forming a repeating “ABA- ” pattern, where “A ” and “B ” denote tones of different frequencies, and “- ” denotes a silent gap. Each sequence contained twenty “ABA ” triplets, for a total duration of 10 s. Each tone was 125 ms long, including 20-ms raised-cosine onset and offset ramps. The inter-triplet gap was 125 ms. The main stimulus parameter was the Frequency Difference, ∆F, between the A and B tones, which varied from 1 to 9 semitones (1 semitone = 6 % Frequency Difference), with intermediate values of 3 and 6 semitones. In the neurophysiological experiments, the level of the tones was set to 75 dB SPL and each sequence was presented 20 times to the neuron, in random order, with a silent pause of 5 s between consecutive sequences. Additional Frequency Differences of 0 and 15 semitones were also sometimes used, as well as negative ∆Fs. Physiology. Twenty three pigmented guinea pigs (Cavia porcellus) were anaesthetized with urethane (1 g/kg, ip). Hypnorm (fentanyl/fluanisone) was administered as supplementary analgesia (1 mg/kg, im). Anaesthesia and analgesia were maintained at a depth sufficient to abolish the pedal withdrawal reflex (front paw). Additional doses of Hypnorm (1 ml/kg) or urethane (1 ml) were administered on indication. Surgica

  • characterizing the dependence of pure tone Frequency Difference limens on Frequency duration and level
    Hearing Research, 2012
    Co-Authors: Christophe Micheyl, Li Xiao, Andrew J Oxenham
    Abstract:

    This study examined the relationship between the Difference limen for Frequency (DLF) of pure tones and three commonly explored stimulus parameters of Frequency, duration, and sensation level. Data from 12 published studies of pure-tone Frequency discrimination (a total of 583 DLF measurements across 77 normal-hearing listeners) were analyzed using hierarchical (or “mixed-effects”) generalized linear models. Model parameters were estimated using two approaches (Bayesian and maximum likelihood). A model in which log-transformed DLFs were predicted using a sum of power-law functions plus a random subject- or group-specific term was found to explain a substantial proportion of the variability in the psychophysical data. The results confirmed earlier findings of an inverse-square-root relationship between log-transformed DLFs and duration, and of an inverse relationship between log(DLF) and sensation level. However, they did not confirm earlier suggestions that log(DLF) increases approximately linearly with the square-root of Frequency; instead, the relationship between Frequency and log(DLF) was best fitted using a power function of Frequency with an exponent of about 0.8. These results, and the comprehensive quantitative analysis of pure-tone Frequency discrimination on which they are based, provide a new reference for the quantitative evaluation of models of Frequency (or pitch) discrimination.

  • further evidence that fundamental Frequency Difference limens measure pitch discrimination
    Journal of the Acoustical Society of America, 2012
    Co-Authors: Christophe Micheyl, Claire Ryan, Andrew J Oxenham
    Abstract:

    Difference limens for complex tones (DLCs) that differ in F0 are widely regarded as a measure of periodicity-pitch discrimination. However, because F0 changes are inevitably accompanied by changes in the frequencies of the harmonics, DLCs may actually reflect the discriminability of individual components. To test this hypothesis, DLCs were measured for complex tones, the component frequencies of which were shifted coherently upward or downward by ΔF = 0%, 25%, 37.5%, or 50% of the F0, yielding fully harmonic (ΔF = 0%), strongly inharmonic (ΔF = 25%, 37.5%), or odd-harmonic (ΔF = 50%) tones. If DLCs truly reflect periodicity-pitch discriminability, they should be larger (worse) for inharmonic tones than for harmonic and odd harmonic tones because inharmonic tones have a weaker pitch. Consistent with this prediction, the results of two experiments showed a non-monotonic dependence of DLCs on ΔF, with larger DLCs for ΔF’s of ±25% or ±37.5% than for ΔF’s of 0 or ±50% of F0. These findings are consistent with ...

  • further evidence that fundamental Frequency Difference limens measure pitch discrimination
    Journal of the Acoustical Society of America, 2012
    Co-Authors: Christophe Micheyl, Claire Ryan, Andrew J Oxenham
    Abstract:

    Difference limens for complex tones (DLCs) that differ in F0 are widely regarded as a measure of periodicity-pitch discrimination. However, because F0 changes are inevitably accompanied by changes in the frequencies of the harmonics, DLCs may actually reflect the discriminability of individual components. To test this hypothesis, DLCs were measured for complex tones, the component frequencies of which were shifted coherently upward or downward by ΔF = 0%, 25%, 37.5%, or 50% of the F0, yielding fully harmonic (ΔF = 0%), strongly inharmonic (ΔF = 25%, 37.5%), or odd-harmonic (ΔF = 50%) tones. If DLCs truly reflect periodicity-pitch discriminability, they should be larger (worse) for inharmonic tones than for harmonic and odd harmonic tones because inharmonic tones have a weaker pitch. Consistent with this prediction, the results of two experiments showed a non-monotonic dependence of DLCs on ΔF, with larger DLCs for ΔF’s of ±25% or ±37.5% than for ΔF’s of 0 or ±50% of F0. These findings are consistent with models of pitch perception that involve harmonic templates or with an autocorrelation-based model provided that more than just the highest peak in the summary autocorrelogram is taken into account.

Brian M Worthmann - One of the best experts on this subject based on the ideXlab platform.

  • cross term analysis in Frequency Difference based source localization methods
    Journal of the Acoustical Society of America, 2018
    Co-Authors: Brian M Worthmann, David R Dowling
    Abstract:

    In previous work, it has been shown that a quadratic product of Frequency-domain acoustic fields at different frequencies but the same spatial location leads to an auxiliary field which may contain field information at frequencies below the original signal’s bandwidth (Worthmann, Song and Dowling, 2015, JASA 138, 3549-3562). This quadratic product, termed the Frequency-Difference autoproduct, has been shown to be valuable for beamforming and source localization in the presence of environmental mismatch and/or array sparseness. However, in a multipath environment, this quadratic product leads to undesired cross-terms. Bandwidth averaging procedures have been found to suppress some of their detrimental influences in some cases, but not all. Additionally, the poor dynamic range observed in Frequency-Difference beamforming and Frequency-Difference matched field processing are associated with the imperfect mitigation of these cross-terms. In this presentation, the nature of these cross-terms is analyzed, and signal processing tools are developed which attempt to robustly mitigate the detrimental effects of these cross terms. These signal processing tools can be used to potentially improve localization performance when using Frequency-Difference autoproduct-based source localization schemes. [Sponsored by ONR and NSF]

  • adaptive Frequency Difference matched field processing for high Frequency source localization in a noisy shallow ocean
    Journal of the Acoustical Society of America, 2017
    Co-Authors: Brian M Worthmann, H C Song, David R Dowling
    Abstract:

    Remote source localization in the shallow ocean at frequencies significantly above 1 kHz is virtually impossible for conventional array signal processing techniques due to environmental mismatch. A recently proposed technique called Frequency-Difference matched field processing (Δf-MFP) [Worthmann, Song, and Dowling (2015). J. Acoust. Soc. Am. 138(6), 3549–3562] overcomes imperfect environmental knowledge by shifting the signal processing to frequencies below the signal's band through the use of a quadratic product of Frequency-domain signal amplitudes called the autoproduct. This paper extends these prior Δf-MFP results to various adaptive MFP processors found in the literature, with particular emphasis on minimum variance distortionless response, multiple constraint method, multiple signal classification, and matched mode processing at signal-to-noise ratios (SNRs) from −20 to +20 dB. Using measurements from the 2011 Kauai Acoustic Communications Multiple University Research Initiative experiment, the l...

  • nonlinear signal processing techniques for active sonar localization in the shallow ocean with significant environmental uncertainty and reverberation
    Fourth International Conference on the Effects of Noise on Aquatic Life, 2016
    Co-Authors: Brian M Worthmann, David R Dowling
    Abstract:

    Sonar signal processing techniques based on acoustic models of shallow ocean environments are frequently of limited use for the mid- to high-Frequency regimes typical for active sonar. To make use of acoustical models of the environment, signal processing algorithms typically require better-than-a-wavelength accuracy in the acoustic path estimates. Given this limitation, and practical knowledge that can be expected for shallow ocean environments, model-based signal processing schemes are often limited to frequencies below approximately 1 kHz. This Frequency limitation is overcome by extending a recent passive source localization technique (Frequency Difference matched field processing, see Worthmann et al., JASA 138, 3549-3562, 2015) to monostatic active sonar target localization, where strongly reverberant environments can obscure a desired target echo. The Frequency Difference active sonar technique is presented along with comparisons to existing detection and localization algorithms. Additionally, simu...

  • high Frequency source localization in a shallow ocean sound channel using Frequency Difference matched field processing
    Journal of the Acoustical Society of America, 2015
    Co-Authors: Brian M Worthmann, H C Song, David R Dowling
    Abstract:

    Matched field processing (MFP) is an established technique for locating remote acoustic sources in known environments. Unfortunately, environment-to-propagation model mismatch prevents successful application of MFP in many circumstances, especially those involving high Frequency signals. For beamforming applications, this problem was found to be mitigated through the use of a nonlinear array-signal-processing technique called Frequency Difference beamforming (Abadi et. al. 2012). Building on that work, this nonlinear technique was extended to Bartlett MFP, where ambiguity surfaces were calculated at frequencies two orders of magnitude lower than the propagated signal, where the detrimental effects of environmental mismatch are much reduced. Previous work determined that this technique has the ability to localize high-Frequency broadband sources in a shallow ocean environment with a sparse vertical array, using both simulated and experimental propagation data. Using simulations, the performance of this technique with horizontal arrays and adaptive signal processing techniques was investigated. Results for signals with frequencies from 10 kHz to 30 kHz that propagated in a 100-m-deep shallow ocean sound channel with a downward refracting sound speed profile will be shown for source array ranges of one to several kilometers. [Sponsored by the Office of Naval Research.]

  • high Frequency source localization in a shallow ocean sound channel using Frequency Difference matched field processing
    Journal of the Acoustical Society of America, 2015
    Co-Authors: Brian M Worthmann, H C Song, David R Dowling
    Abstract:

    Matched field processing (MFP) is an established technique for source localization in known multipath acoustic environments. Unfortunately, in many situations, particularly those involving high Frequency signals, imperfect knowledge of the actual propagation environment prevents accurate propagation modeling and source localization via MFP fails. For beamforming applications, this actual-to-model mismatch problem was mitigated through a Frequency downshift, made possible by a nonlinear array-signal-processing technique called Frequency Difference beamforming [Abadi, Song, and Dowling (2012). J. Acoust. Soc. Am. 132, 3018–3029]. Here, this technique is extended to conventional (Bartlett) MFP using simulations and measurements from the 2011 Kauai Acoustic Communications MURI experiment (KAM11) to produce ambiguity surfaces at frequencies well below the signal bandwidth where the detrimental effects of mismatch are reduced. Both the simulation and experimental results suggest that Frequency Difference MFP ca...