High Frequency Components in Bottlenose Dolphin Echolocation Signals.

• Main Author: Toland, Ronald W., Jr
• Other Authors: NAVAL POSTGRADUATE SCHOOL MONTEREY CA
• Format: Text
• Language: English
• Published: 1998
• Subjects: Anatomy and Physiology; Acoustic Detection and Detectors; *HIGH FREQUENCY; *SIGNALS; *ECHO RANGING; *DOLPHINS(MAMMALS); *BIOSONAR; OUTPUT; MEASUREMENT; TARGET RECOGNITION; ENERGY; THESES; REFLECTION; SOUND; ANIMALS; LOSSES; ACOUSTIC FILTERS; REFLECTIVITY; INSERTION LOSS; WHALES; Austin; toothed whales
• Online Access: http://www.dtic.mil/docs/citations/ADA354939; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA354939

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.