10:50
11:05
4aAO8. Differences in whistles of bottlenose dolphins between two populations in southeastern Australia. Michelle Lemon 共Marine Mammal Res. Group, Macquarie Univ., NSW, 2109, Australia兲, Douglas H. Cato 共Defence Sci. and Technol. Organisation, Pyrmont, NSW, 2009, Australia兲, and Robert Harcourt 共Macquarie Univ., NSW, 2109, Australia兲
4aAO9. Verified passive acoustic detection of beaked whales „Mesoplodon densirostris… using distributed bottom-mounted hydrophones in the tongue of the ocean, Bahamas. David Moretti, Ronald Morrissey, Nancy DiMarzio, and Jessica Ward 共Naval Undersea Warfare Ctr. 共NUWC兲, Code 71, Bldg. 1351, Newport, RI 02841兲
The acoustic repertoires of two populations of Indo-Pacific bottlenose dolphins, Tursiops aduncus, have been studied in comparison with surface behaviors in southeast Australia. These populations are largely genetically differentiated and geographically isolated, one being in Port Stephens and the other in Jervis Bay about 300 km to the south. Ten variables were measured from the fundamental frequency of 200 whistle contours from each population, recorded in various behavioral contexts. Principal component analysis revealed significant differences between the populations. The Port Stephens dolphin population have less complex whistles of a higher frequency than those in Jervis Bay. Although significant differences were observed in phonation rates between behaviors at either site, there was no interaction between site and behavior. The genetic difference and degree of isolation of the populations suggest that cultural drift may play a part in the differences in whistles between sites. Ambient noise measured during observations showed significant differences between sites, but the measurements did not fully sample the range of ambient noise and differences are small compared to the expected temporal variation.
Passive detection of beaked whales has become increasingly important as at least two species, Blainville’s beaked whales 共Mesoplodon densirostris兲 and Cuvier’s beaked whales 共Ziphius cavorostris兲 have stranded in events associated with sonar. Passive acoustic detection and localization algorithms develop as part of the Office of Naval Research 共ONR兲 Marine Mammal Monitoring on Navy Range 共M3R兲 program will be presented along with results from a series of tests that demonstrate the efficacy of passive acoustic detection of vocalizing M. densirostris. Ninety-two bottom-mounted sensors at the Atlantic Undersea Test and Evaluation Center 共AUTEC兲 were monitored for vocalizations. M3R systems were used to detect and localize vocalizing animals. Based on these real-time data, trained observers were vectored to the animals and verified the species. Focal follows coordinated with passive acoustics were completed. Observer photos along with raw sensor, detection and localization data were collected.
THURSDAY MORNING, 8 JUNE 2006
BALLROOM A, 8:00 A.M. TO 12:00 NOON Session 4aBB
Biomedical UltrasoundÕBioresponse to Vibration and Physical Acoustics: Celebration Session for Edwin Carstensen I Lawrence A. Crum, Cochair Univ. of Washington, Applied Physics Lab., 1013 NE 40th St., Seattle, WA 98105-6698 Diane Dalecki, Cochair Univ. of Rochester, Dept. of Biomedical Engineering, Rochester, NY 14627
Chair’s Introduction—8:00
Invited Papers
8:05 4aBB1. Tissue-ultrasound interactions: Absorption to imaging artifacts. Frederick Kremkau 共Ctr. for Medical Ultrasound, Wake Forest Univ. School of Medicine, Winston-Salem, NC 27157-1039,
[email protected]兲 Attenuation determines fundamental limitations in sonography. It directly limits the imaging depth 共penetration兲 and indirectly limits the detail, contrast, and temporal resolutions by limiting the frequency. These resolutions improve with increasing frequency but penetration requirements determine the upper limit on frequency in each imaging situation because attenuation 共and therefore penetration兲 is frequency dependent. Attenuation in soft tissue is dominated by absorption 共typically about 90%兲. Absorption occurs primarily at the molecular level. Sonographic artifacts occur when one of the pulse-echo imaging assumptions is violated. These assumptions are that sound travels in straight lines, that echoes originate only from objects located on the beam axis, that the amplitude of returning echoes is related directly to the reflecting or scattering properties of distant objects, and that the distance to these objects is proportional to the round-trip travel time 共13 s/cm of depth兲. If scattering strength of an object is high but its absorption is low, a hyperechoic presentation will occur with distal enhancement. A more common occurrence is hyperechoic with distal shadow indicating high echogenicity and attenuation, therefore high absorption. Examples of several imaging artifacts will be shown with discussion of the propagation assumptions violated. 3374
J. Acoust. Soc. Am., Vol. 119, No. 5, Pt. 2, May 2006
151st Meeting: Acoustical Society of America 2006
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