Using a coherent hydrophone array for observing sperm whale range, classification, and shallow-water dive profiles

Abstract

Sperm whales in the New England continental shelf and slope were passively localized, in both range and bearing, and classified using a single low-frequency (<2500 Hz), densely sampled, towed horizontal coherent hydrophone array system. Whale bearings were estimated using time-domain beamforming that provided high coherent array gain in sperm whale click signal-to-noise ratio. Whale ranges from the receiver array center were estimated using the moving array triangulation technique from a sequence of whale bearing measurements. Multiple concurrently vocalizing sperm whales, in the far-field of the horizontal receiver array, were distinguished and classified based on their horizontal spatial locations and the inter-pulse intervals of their vocalized click signals. The dive profile was estimated for a sperm whale in the shallow waters of the Gulf of Maine with 160 m water-column depth located close to the array's near-field where depth estimation was feasible by employing time difference of arrival of the direct and multiply reflected click signals received on the horizontal array. By accounting for transmission loss modeled using an ocean waveguide-acoustic propagation model, the sperm whale detection range was found to exceed 60 km in low to moderate sea state conditions after coherent array processing.

Review of Underwater and In-Air Sounds Emitted by Australian and Antarctic Marine Mammals

“…Sperm whales have been recorded off the US east coast [324][325][326][327][328], off Nova Scotia [329,330], around the Bahamas [331][332][333], around Bermuda [334], in the Caribbean [335][336][337][338][339], in the Gulf of Mexico [340][341][342][343], in Alaska [344][345][346][347][348], in the northeast Pacific [349], off Japan [350,351] around Hawaii [352], at the Galapagos Islands [173,353,354], at the Azores [355], off Scotland [356], off Norway [357][358][359][360][361], in the Mediterranean [362][363][364][365][366], in the South Pacific [367], in New Zealand [368][369]<...>…”

Comparing Performances of Five Distinct Automatic Classifiers for Fin Whale Vocalizations in Beamformed Spectrograms of Coherent Hydrophone Array

“…The horizontal beamwidth of the array is a function of the array aperture length L, steering angle φ, as well as center frequency f c and bandwidth B of the signal [39][40][41]. The 1 dB angular width β 1dB (φ, f c ) [10] of the receiver array for the fin whale 20 Hz pulse and 130 Hz upsweep vocalizations are provided in Table 1. The steering angle φ is measured as the horizontal azimuthal angle from array broadside.…”

“…A large-aperture densely-populated coherent hydrophone array system typically detects hundreds of thousands to millions of acoustic signals in the 10 Hz to 4000 Hz frequency range for each day of observation in a continental shelf ocean via the passive ocean acoustic waveguide remote sensing (POAWRS) technique [1,2]. The acoustic signal detections include both broadband transient and narrowband tonal signals from a wide range of natural and man-made sound sources [3][4][5][6][7], such as marine mammal vocalizations [1,2,[8][9][10][11], fish grunts, ship radiated sound [12,13], and seismic airgun signals [14]. Here, we focus our efforts on developing automatic classifers for fin whale vocalizations detected in the Norwegian and Barents Seas during our Norwegian Sea 2014 Experiment (NorEx14) [1].…”

Linearized two-hydrophone localization of a pulsed acoustic source in the presence of refraction: Theory and simulations

“…Whale research largely relies on acoustics. Detection and localization of cetaceans can be carried out either by passive techniques based on the analysis of clicks, impulsive sounds emitted by the whales, received at a hydrophone array (Watkins and Schevill, 1972;Wahlberg et al, 2001;Teloni, 2005;Tran et al, 2014), or by active methods including the use of active sonar (Papastavrou et al, 1989) and tagging (Watkins et al, 1999;Madsen et al, 2002;Johnson and Tyack, 2003;Mathias et al, 2012), or by a combination of the above (Watkins et al, 1993, Zimmer et al, 2003. Passive acoustic monitoring is the most discreet observing method, provided that the animal of interest vocalizes within the range of the receiving instruments, typically on the order of 5-10 km for sperm whales (Goold and Jones, 1995;Jaquet et al, 2001).…”

“…By combining bearing estimates from multiple hydrophone pairs, range, and depth estimates can be obtained (Baggenstoss, 2011). Multi-element arrays (Teloni, 2005;Tran et al, 2014) have the advantage of SNR improvement through beamforming and also allow for localization, e.g., by using backpropagation techniques (Voltz and Lu, 1994) or by combining bearing measurements from spatially separated apertures (Tran et al, 2014). A pair of hydrophones does not have these advantages, but, on the other hand, represents a simple, robust, and low-cost configuration.…”