The array invariant

Abstract

A method is derived for instantaneous source-range estimation in a horizontally stratified ocean waveguide from passive beam-time intensity data obtained after conventional plane-wave beamforming of acoustic array measurements. The method has advantages over existing source localization methods, such as matched field processing or the waveguide invariant. First, no knowledge of the environment is required except that the received field should not be dominated by purely waterborne propagation. Second, range can be estimated in real time with little computational effort beyond plane-wave beamforming. Third, array gain is fully exploited. The method is applied to data from the Main Acoustic Clutter Experiment of 2003 for source ranges between 1 to 8 km, where it is shown that simple, accurate, and computationally efficient source range estimates can be made.

Diel and Spatial Dependence of Humpback Song and Non-Song Vocalizations in Fish Spawning Ground

“…The humpback non-song vocalizations, dominated by shorter duration D-and B-moans, as well as a small fraction of longer duration cries, are found to have significantly larger mean and more variable inter-pulse intervals of 14.2 ± 11 s. The non-song vocalizations were detected at night with negligible detections during the day, implying they probably function as nighttime communication or contact signals. The humpback song and non-song vocalizations are separately localized using the moving array triangulation [2,9,10] and array invariant techniques [2,[9][10][11]. The humpback song and non-song moan calls are found to be consistently localized to a dense area on northeastern Georges Bank and a less dense region extended from Franklin Basin to the Great South Channel.…”

“…The horizontal location of each marine mammal vocalization consists of range and bearing estimates. The moving array triangulation (MAT) [2,9,10] and the array invariant (AI) [2,[9][10][11] methods are applied to determine the range of the vocalizations from the horizontal receiver array centre. Position estimation error, or the root mean squared (RMS) distance between the actual and estimated location, is a combination of range and bearing errors quantified for this array in [2,[9][10][11].…”

“…The moving array triangulation (MAT) [2,9,10] and the array invariant (AI) [2,[9][10][11] methods are applied to determine the range of the vocalizations from the horizontal receiver array centre. Position estimation error, or the root mean squared (RMS) distance between the actual and estimated location, is a combination of range and bearing errors quantified for this array in [2,[9][10][11]. Range estimation error, expressed as the percentage of the range from the source location to the horizontal receiver array centre, for the MAT technique is roughly 2% at array broadside and gradually increases to 10% at 65 • from broadside and 25% at 90 • from broadside, that is, near or at endfire [9].…”

“…The humpback song and non-song vocalization sequences are localized from their measured bearing versus time trajectories by employing the moving array triangulation [2,9,10] and the array invariant [2,[9][10][11] techniques. The humpback song and non-song vocalization rate spatial distributions are overlain with the spatial distribution of their fish prey, the Atlantic herring.…”

Vocalization Source Level Distributions and Pulse Compression Gains of Diverse Baleen Whale Species in the Gulf of Maine

“…The source level of each baleen whale vocalization is estimated from the received vocalization pressure level by compensating for corresponding broadband transmission loss [1,[16][17][18] from whale location to the receiver array center location [19][20][21] in the temporally-and spatially-varying Gulf of Maine environment. The whale locations for each species were previously determined using the moving array triangulation [2,22,23], the bearings-migration minimum mean square error and the array invariant techniques [2,[22][23][24] from the measured bearing versus time trajectories of sequences of vocalizations from that species [1]. The marine mammal species-dependent vocalization source level is an important parameter for estimating the marine mammal detection region for a given species in any passive underwater acoustic sensing system [1,2,25].…”