Volume 128, Issue 1, July 2010
Index of content:
- BIOACOUSTICS 
128(2010); http://dx.doi.org/10.1121/1.3442362View Description Hide Description
This study provides a comprehensive description of the acoustic characteristics of the predominant long-range underwater vocalizations of the crabeater seal, Lobodon carcinophaga, derived from stationary and continuous long-term recordings obtained in the Southern Ocean in 2007. Visual screening of data recorded between 1 October and 15 December 2007 indicates that the principal period of vocal activity of the crabeater seal is the latter part of October and all of November, coinciding with the breeding season of this species. Two call types were identified during this period: the low moan call, which has been described in previous studies and the high moan call, a call type newly described here. Out of 17 052 manually extracted crabeater seal calls, high-quality recordings of 152 low moans and 86 high moans with a signal-to-noise ratio exceeding 15 dB were selected and call-specific acoustic features were determined. While the mean duration of the two call types was comparable , the high moan occurred at notably higher frequencies (1000–4900 Hz) than the low moan (260–2500 Hz). This study provides baseline information necessary to develop automated detection algorithms to facilitate systematic screening of extended data sets for crabeater seal vocalizations.
128(2010); http://dx.doi.org/10.1121/1.3442361View Description Hide Description
Egg white, a protein-containing solution, is characterized as a blood coagulation surrogate for the acoustical and thermal evaluation of therapeutic ultrasound, especially high intensity focused ultrasound (HIFU) devices. Physical properties, including coagulation temperature, frequency dependent attenuation, sound speed, viscosity, and thermal properties, were measured as a function of temperature . Thermal coagulation and attenuation (5–12 and 1 MHz) of cow blood, pig blood, and human blood also were assessed and compared with egg white. For a 30 s thermal exposure, both egg white and blood samples (3 mm thickness) started to denature at and coagulate into an elastic gel at . The attenuation of egg white was found to be similar to that of the blood samples, having values of , , and at 20, 75, and , respectively. This significant attenuation increase with temperature was determined to be caused mainly by bubble cavity formation. The other temperature-dependent parameters are also similar to the reported values for blood. These properties make egg white a potentially useful bench testing tool for the safety and efficacy evaluation of therapeutic ultrasound devices.
128(2010); http://dx.doi.org/10.1121/1.3446099View Description Hide Description
Vocalizations of blue whales were recorded with a cabled hydrophone array at Pioneer Seamount, 50 miles off the California coast. Most calls occurred in repeated sequences of two-call pairs ( , then ). The call is a frequency-modulated tone highly repeatable in form and pitch. A model of this sound is described which permits detecting very small frequency shifts. calls are found to be aligned in frequency to about one part in 180. This requires very fine pitch discrimination and control over calling frequency, and suggests that synchronizing to a common frequency pattern carries some adaptive advantage. Some possibilities for acoustic sensing by whales requiring this fine frequency resolution are discussed.