Local acoustic particle motion guides sound-source localization behavior in the plainfin midshipman fish, Porichthys notatus (PDF)

Zeddies, D.G., R.R. Fay, M.D. Gray, P.W. Alderks, A. Acob, and J.A. Sisneros

Journal of Experimental Biology 215: 152-160 (2012)

DOI: 10.1242/jeb.064998

Sound-source localization behavior was studied in the plainfin midshipman fish (Porichthys notatus) by making use of the naturally occurring phonotaxis response of gravid females to playback of the male's advertisement call. The observations took place outdoors in a circular concrete tank. A dipole sound projector was placed at the center of the tank and an 80–90 Hz tone (the approximate fundamental frequency to the male's advertisement call) was broadcast to gravid females that were released from alternative sites approximately 100 cm from the source. The phonotaxic responses of females to the source were recorded, analyzed and compared with the sound field. One release site was approximately along the vibratory axis of the dipole source, and the other was approximately orthogonal to the vibratory axis. The sound field in the tank was fully characterized through measurements of the sound pressure field using hydrophones and acoustic particle motion using an accelerometer. These measurements confirmed that the sound field was a nearly ideal dipole. When released along the dipole vibratory axis, the responding female fish took essentially straight paths to the source. However, when released approximately 90 deg to the source's vibratory axis, the responding females took highly curved paths to the source that were approximately in line with the local particle motion axes. These results indicate that the acoustic cues used by fish during sound-source localization include the axes of particle motion of the local sound field.

Mapping cumulative noise from shipping to inform marine spatial planning (PDF)

Erbe, C., A.O. MacGillivray, and R. Williams

Journal of the Acoustical Society of America 132(5): EL423-EL428 (2012)

DOI: 10.1121/1.4758779

Including ocean noise in marine spatial planning requires predictions of noise levels on large spatiotemporal scales. Based on a simple sound transmission model and ship track data (Automatic Identification System, AIS), cumulative underwater acoustic energy from shipping was mapped throughout 2008 in the west Canadian Exclusive Economic Zone, showing high noise levels in critical habitats for endangered resident killer whales, exceeding limits of “good conservation status” under the EU Marine Strategy Framework Directive. Error analysis proved that rough calculations of noise occurrence and propagation can form a basis for management processes, because spending resources on unnecessary detail is wasteful and delays remedial action.

Tracking of Pacific walruses in the Chukchi Sea using a single hydrophone (PDF)

Mouy, X., D.E. Hannay, M.M. Zykov, and B. Martin

Journal of the Acoustical Society of America 131: 1349-1358 (2012)

DOI: 10.1121/1.3675008

The vocal repertoire of Pacific walruses includes underwater sound pulses referred to as knocks and bell-like calls. An extended acoustic monitoring program was performed in summer 2007 over a large region of the eastern Chukchi Sea using autonomous seabed-mounted acoustic recorders. Walrus knocks were identified in many of the recordings and most of these sounds included multiple bottom and surface reflected signals. This paper investigates the use of a localization technique based on relative multipath arrival times (RMATs) for potential behavior studies. First, knocks are detected using a semi-automated kurtosis-based algorithm. Then RMATs are matched to values predicted by a ray-tracing model. Walrus tracks with vertical and horizontal movements were obtained. The tracks included repeated dives between 4.0 m and 15.5 m depth and a deep dive to the sea bottom (53 m). Depths at which bell-like sounds are produced, average knock production rate and source levels estimates of the knocks were determined. Bell sounds were produced at all depths throughout the dives. Average knock production rates varied from 59 to 75 knocks/min. Average source level of the knocks was estimated to 177.6 ± 7.5 dB re 1 μPa peak @ 1 m.