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We investigate the impact of low-rank interference on the problem of distinguishing between two seabed types using ambient sound as an acoustic source. The resulting frequency-domain snapshots follow a zero-mean, circularly-symmetric Gaussian distribution, where each seabed type has a unique covariance matrix. Detecting changes in the seabed type across distinct spatial locations can be formulated as a two-sample hypothesis test for equality of covariance, for which Box's M-test is the classical solution. Interference sources such as passing ships result in additive noise with a low-rank covariance that can reduce the performance of hypothesis testing. We first present a method to construct a worst-case interference field, making hypothesis testing as difficult as possible. We then provide an alternating optimization procedure to recover the interference-free covariance matrix. Experiments on synthetic data show that the optimized interferer can greatly reduce hypothesis testing performance, while our recovery method perfectly eliminates this interference for a sufficiently small interference rank. On real data from the New England Shelf Break Acoustics experiment, we show that our approach successfully mitigates interference, allowing for accurate hypothesis testing and improving bottom loss estimation.
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Retrieval of Dispersion Dependences of Waveguide Modes from Ship Noise Measurements Using Two Synchronized Arrays
Abstract —An approach is proposed for estimating the dispersion characteristics of waveguide modes from analysis of ship noise recorded by two closely spaced and synchronized vertical arrays. This approach was used for an experimental study of the mode structure of a low-frequency sound field in a shallow-water waveguide with a gas-saturated bottom in a wide frequency band (from 20 to 250 Hz). The experiment was carried out in Lake Kinneret (Israel), known for its high methane bubble content in the sedimentary layer (~1%) and, consequently, for the low sound speed in this layer (~100 m/s). The maximum depth in the area of the experiment was 40.4 m. The receiving system consisted of two 27 m vertical arrays spaced 40 m from each other and covering part of the waveguide below the thermocline. The noise source, the R/V Hermona , moved along a straight line connecting the arrays at distances of up to 1 km from them. The approach made it possible to isolate the frequency dependences of the phase velocities for the first 12 modes; these dependences proved close to those for a waveguide with an perfectly soft bottom, except for the frequency region near the cutoff frequency. The limitations and possible development of the technique are discussed.
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- Award ID(s):
- 1657430
- PAR ID:
- 10337874
- Date Published:
- Journal Name:
- Acoustical Physics
- ISSN:
- 1063-7710
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1134/S1063771022040133
