A free‐drifting 14‐sonobuoy array was used to localize North Atlantic right whales (Eubalaena glacialis) in the Grand Manan Basin area of the Bay of Fundy. This area is a primary summer/autumn right whale habitat and overlaps an international shipping lane. The three‐hour deployment on a single day provided two‐dimensional localization of 94 right whale sounds based on arrival time differences determined from spectrogram cross‐correlation analysis. The sounds were of two distinct types: tonal and gunshot. Maximum detection distances were about 30 km for both types of sound. The mean RMS location error was 1.8 km for tonal‐type sounds and 2.5 km for gunshot‐type sounds. The average RMS error was 20% of the average distance from the receiving hydrophones, the primary source of error being uncertainty in the sonobuoy positions.

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During a sea trial on the Scotian Shelf, acoustic signals from a sonic boom were recorded on 11 hydrophones of a vertical array. The array spanned the lower 50 m of the water column above a sand bank at 76 m water depth. The source of the sonic boom was deduced to be a Concorde supersonic airliner traveling at about Mach 2. The waterborne waveform was observed to decay as an evanescent wave below the sea surface, as expected. The calm weather (sea state 1) resulted in low ambient noise and low self-noise at the hydrophones, and good signal-to-noise ratio on the upper hydrophones; however, the decreased signal amplitude is more difficult to detect towards the lower part of the water column. The period of the observed waveform is of the order 0.23 s, corresponding to a peak frequency of about 3 Hz. The shape of the measured waveform differs noticeably from the theoretical N-shape waveform predicted with Sawyers' theory [J. Acoust. Soc. Am. 44, 523-524 (1968)]. A simple shallow-ocean geoacoustic model suggests that this effect may be caused in part by seismo-acoustic interaction of the infrasonic waves with the elastic sediments that form the seabed.

During a sea trial on the Scotian Shelf, acoustic signals from a sonic boom were recorded on several hydrophones of a vertical array. The array spanned the lower 50 m of the water column above a sand bank at 75-m water depth. The source of the sonic boom was deduced to be a Concorde supersonic airliner traveling at about Mach 2. The water-borne waveform was observed to decay as an evanescent wave below the sea surface, as expected. The very calm weather resulted in low ambient noise and low self-noise at the hydrophones, resulting in good signal-to-noise ratio on the upper hydrophones; however, the decreased signal amplitude is more difficult to detect towards the lower part of the water column. The period of the observed waveform is of the order 0.25 s, corresponding to a peak frequency of about 4 Hz. The shape of the measured waveform differs slightly from the theoretical N-shape waveform predicted with Sawyers theory [J. Acoust. Soc. Am. 44, 523–524 (1968)]. A simple shallow ocean geoacoustic model suggests that this effect may be caused by seismo-acoustic interaction of the infrasonic waves with the elastic sediments that form the seabed.

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