The Airy phase of explosive sounds in shallow water

Wan, Lin; Badiey, Mohsen; Knobles, David P.; Wilson, Preston S.

doi:10.1121/1.5026023

Cited by 29 publications

(13 citation statements)

References 11 publications

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“…Group speed estimates based on the pressure channel [see Fig. 9(a)] suggest a frequency of the Airy phase for mode 2 at 28 Hz, which is in agreement with that recently reported by Wan et al [4]; additionally, we report an Airy phase group speed for mode 2 equal to 1328 m/s (median), with a 25th-75th percentile range of 1326-1333 m/s. However, signal-to-noise limitations prevented estimates of the Airy phase for modes 3 and 4.…”

Section: Resultssupporting

confidence: 92%

“…We emphasize that the notional geoacoustic model is not a result of an inversion per se but instead meant as a nominally consistent representation of available ground truth data in terms of water depth measured at IVAR (mean depth, 74.4 m), measured water sound speed c w , and approximate mud-layer thickness at the IVAR site based high-resolution chirp acoustic reflection data [1]. Some experimentation with forward modeling is required to establish parameters for the mud layer, a key component of the notional geoacoustic model, and we use values consistent with those emerging from recently published studies [2], [4], such as mud-layer thickness and linear sound-speed gradient equal to 10 s −1 . We first undertake a brief analysis of sediment attenuation to confirm that the attenuation parameters (see Table I) are at least nominally consistent with the data.…”

Section: E Comparison Of Model Results Based On Two Geoacoustic Modelsmentioning

confidence: 99%

“…shortly before recovery of IVAR shows a relatively well-mixed water column typical of other observations made during SBCEX [4]. In our subsequent manipulation of vector acoustic data, we implement the depth average as representing an isovelocity water column, with sound speed c w = 1468.3 m/s.…”

Section: Ivar System and Deployment During Sbcexmentioning

confidence: 91%

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Vector Acoustic Analysis of Time-Separated Modal Arrivals From Explosive Sound Sources During the 2017 Seabed Characterization Experiment

Dahl

Dall’Osto

2020

IEEE J. Oceanic Eng.

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The Intensity Vector Autonomous Recorder (IVAR) is a system that records four coherent channels of acoustic data continuously: one channel for acoustic pressure and three channels associated with a triaxial accelerometer from which acoustic particle velocity is obtained. IVAR recorded the vector acoustic field in broadband signals originating from Signal, Underwater Sound (SUS) (Mk-64) charges deployed at 5-13-km range from the fixed IVAR site (mean depth 74.4 m) as part of the 2017 Seabed Characterization Experiment (SBCEX) designed to study the acoustics of fine-grained muddy sediments. Sufficient geometric dispersion at these ranges permitted unambiguous identification of up to four modes as a function of frequency for frequencies less than 80 Hz. From time-frequency analysis of the dispersed arrivals, a single mode (n) and single-frequency (f i) properties are identified at peaks in the narrowband scalar field, with time dependence corresponding to mode group speed. At these time-frequency addresses, four quantities derived from the vector acoustic measurements are formed by coherent combination of pressure and velocity channels: first, modal phase speed; second, circularity, a measure of the normalized curl of active intensity; third, depth-dependent mode speed of energy; and fourth, vertical component of reactive intensity normalized by scalar intensity. A means to compute these quantities theoretically is provided, and a comparison of model results based on a notional geoacoustic representation for the SBCEX experimental area consisting of a single low-speed mud layer over a half-space area versus a Pekeris representation based on the same half-space shows a striking difference, with the field observations also clearly at variance with the Pekeris representation. A fundamental property of mode 2, observed at the IVAR location, is a change in sign for circularity and vertical reactive intensity near 37 Hz that is posited as a constraint observation for mode 2 that must be exhibited by any geoacoustic model that includes a low-speed mudlike layer applied to this location.

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Section: Resultssupporting

confidence: 92%

Section: E Comparison Of Model Results Based On Two Geoacoustic Modelsmentioning

confidence: 99%

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Vector Acoustic Analysis of Time-Separated Modal Arrivals From Explosive Sound Sources During the 2017 Seabed Characterization Experiment

Dahl

Dall’Osto

2020

IEEE J. Oceanic Eng.

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“…Hence, a definitive conclusion on the authenticity of the low velocity/density layer is not possible without deep coring. However, it would be interesting to compare this result with inversions that take into account the mode Airy phase of low order modes (e.g., [19]). Indeed, both Airy phase and the high order modes that are used here are sensitive to features deep below the seabed.…”

Section: B Inversion Resultsmentioning

confidence: 99%

“…Modal travel times have been used recently for geoacoustic inversion in the SBCEX context by Wan et al [19] and Bonnel et al [20]. The first study [19] considered a (relatively) long range (r ∼ 15 km), so that the low-frequency components (f < 80 Hz) of the first 4 modes were resolved on conventional TF representations. The second study [20] was performed at shorter range (r ∼ 5 km), and warping was used to resolve up to mode number 18 over the frequency band 20-440 Hz.…”

Section: Introductionmentioning

confidence: 99%

Trans-Dimensional Inversion of Modal Dispersion Data on the New England Mud Patch

Bonnel¹,

Dosso²,

Eleftherakis³

et al. 2020

IEEE J. Oceanic Eng.

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This paper presents single receiver geoacoustic inversion of two independent data sets recorded during the 2017 seabed characterization experiment on the New England Mud Patch. In the experimental area, the water depth is around 70 m, and the seabed is characterized by an upper layer of fine grained sediments with clay (i.e., mud). The first data set considered in this paper is a combustive sound source signal, and the second is a chirp emitted by a J15 source. These two data sets provide differing information on the geoacoustic properties of the seabed, as a result of their differing frequency content, and the dispersion properties of the environment. For both data sets, source/receiver range is about 7 km, and modal time-frequency dispersion curves are estimated using warping. Estimated dispersion curves are then used as input data for a Bayesian trans-dimensional inversion algorithm. Subbottom layering and geoacoustic parameters (sound speed and density) are thus inferred from the data. This paper highlights important properties of the mud, consistent with independent in situ measurements. It also demonstrates how information content differs for two data sets collected on reciprocal tracks, but with different acoustic sources and modal content. Index Terms-Geoacoustic inversion, New England mud patch, seabed characterization experiment (SBCEX), underwater acoustics, warping.

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An Efficient Wave Approach for Simulating the Propagation of Impulsive Signals in Hydroacoustic Waveguides on the Sea Shelf

Lisyutin

Yaroshenko

Lastovenko

2021

IOP Conf. Ser.: Earth Environ. Sci.

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The paper proposes an efficient wave method for simulating the propagation of impulsive signals in hydroacoustic waveguides of the sea shelf. The method of normal modes calculates the acoustic field in a wide frequency band. Then the inverse Fourier transform of the acoustic field is performed and the impulse response of the waveguide is restored. The signal replica is then calculated as a convolution of the impulse response and the signal. The advantages of this approach are as follows. Convolution is cyclical – there are no restrictions on the duration of the signal. Not only calculated, but also experimentally determined impulse response can be used. At the discretion of the researcher, the fields of individual modes can be excluded, add noise in the frequency or time domain, simulate the movement of the source, the impact of wind waves. Restriction - conditions for uniformity of the waveguide along the distance. A number of examples are considered, in which the possibility of determining the acoustic properties of the bottom is studied.

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The Airy phase of explosive sounds in shallow water

Cited by 29 publications

References 11 publications

Vector Acoustic Analysis of Time-Separated Modal Arrivals From Explosive Sound Sources During the 2017 Seabed Characterization Experiment

Vector Acoustic Analysis of Time-Separated Modal Arrivals From Explosive Sound Sources During the 2017 Seabed Characterization Experiment

Trans-Dimensional Inversion of Modal Dispersion Data on the New England Mud Patch

An Efficient Wave Approach for Simulating the Propagation of Impulsive Signals in Hydroacoustic Waveguides on the Sea Shelf

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