Geoacoustic inversion of tow-ship noise via near-field matched-field processing

Abstract

The estimation of geoacoustic parameters of marine sediments and sub-sediment layers involves the measurement of acoustic fields in the ocean waveguide for comparison with accurate forward propagation models. This paper discusses self-noise geoacoustic inversion of tow-ship noise data acquired via a horizontal towed array from the standpoint of near-field matched-field processing (MFP). In particular, the sensitivity of the reconstructed source power to perturbations in the parameters of a short-range propagation model are quantified. Through simulations and experimental results, it is shown that even very quiet ships radiate sufficient noise power to enable self-noise inversion of basic geoacoustic parameters such as effective bottom velocity. The experimental results presented are particularly encouraging in view of the high level of interference shown to be tolerated from nearby shipping.

Sequential vs batch processing of ship noise data in inversion for geoacoustic properties

“…The noise field due to a moving ship can provide diverse observables for environmental characterization [7], [8]. The vertical waveguide impedance as defined by the ratio of pressure and pressure gradient are favored [9], which is shown to be source spectrum independent and highly correlated with environmental properties.…”

Bayesian geoacoustic inversion of ship noise on a horizontal array

“…The use of a towed HLA offers an advantage over moored arrays in terms of system mobility. However, factors such as low signal-to-noise ratio ͑SNR͒ of tow-ship noise 9 and limitations on source-receiver separations ͑hence limited sampling of the acoustic angular spectrum͒ can limit the information in such data. The use of moored arrays and noise from ships of opportunity allows for unobtrusive geoacoustic characterization, and has further advantages in terms of simplicity and economy ͑i.e., a dedicated ship is not required͒.…”

“…Much work on MFI has been performed using high-level acoustic sources and vertical line arrays of sensors. [1][2][3][4][5][6][7] Recent interest has expanded to include applications to data from towed [8][9][10][11] and bottom-moored [12][13][14] horizontal line arrays ͑HLAs͒, and the use of alternative sound sources such as noise from the tow ship received on a towed array, 9,10 or from ships of opportunity received on moored arrays. 15,16,13 The use of ship noise in both cases reduces environmental impact over a controlled source.…”

Seabed Characterization Using Acoustic Communication Signals on an Autonomous Underwater Vehicle With a Thin-Line Towed Array

“…Recently, the source and receiving array have been miniaturized and deployed on an autonomous underwater vehicle (AUV) [4]- [6]. Instead of a dedicated sound source, sources of opportunity, such as the self-noise of the tow ship, have been used in conjunction with a matched-field technique to achieve a model-based inversion of the sediment strata [7]. In this paper, Manuscript a robust measurement of the seabed-reflection loss, using the self-noise of an AUV, towing a thin-line horizontal array, is demonstrated.…”