High frequency components in bottlenose dolphin echolocation signals
By:  Ronald W. Toland, Jr
Publisher: Naval Postgraduate School; Available from National Technical Information Service
Published: 1998
Place of publication: Monterey, Calif; Springfield, Va
Language: eng
Number of pages: 60
Description: The research described in this thesis is a continuation of work started by the Applied Research Laboratories of the University of Texas at Austin into the analysis of biosonar signals. Experiments conducted in 1997 on two species of small toothed whales found these species to emit significant high frequency signal components, extending to as high as 400 to 500 kHz. To assess the importance of these high frequencies in dolphin echolocation and target identification, experiments were performed in which an acoustic filter, used to suppress the high frequencies, was placed between a dolphin and a target. Insertion Loss and Reflection Loss measurements performed on 1/4" thick and 1/2" thick Sound Absorbing Filters (SOAB) demonstrated their effectiveness at absorbing high frequencies above 150 kHz, with little reflectivity. The results from one echolocation experiment, with one dolphin, showed the animal's ability to classify targets was essentially unaffected by the insertion of the filters. Analysis of the dolphin's echolocation signals showed the animal definitely compensating for the filters, by increasing its sound energy output, especially at frequencies above 100 kHz. It is anticipated that this initial experiment will lead to future research in explaining the existence of these high frequency echolocation components.
Notes: "september 1998."

Thesis advisor(s): Thomas G. Muir, Steven R. Baker.

Thesis (M.S. in Engineering Acoustics) Naval Postgraduate School, September 1998.

Includes bibliographical references (p. 58).

Approved for public release; distribution unlimited.

Also available online.

Mode of access: World Wide Web.

System Requirements: Adobe Acrobat reader.

US Navy (USN) author.

dk/dk cc:9116 11/4/98.