Shizuko Hiryu, Yu Shiori, Tatsuro Hosokawa, Hiroshi Riquimaroux and Yoshiaki
Watanabe (2008): On-board telemetry of emitted sounds from free-flying bats:
compensation for velocity and distance stabilizes echo frequency and
amplitude. J. Comp. Physiol. A 194(9), 841-851.
Abstract: To understand complex sensory?motor behavior related to object
perception by echolocating bats, precise measurements are needed for echoes
that bats actually listen to during flight. Recordings of echolocation
broadcasts were made from flying bats with a miniature light-weight
microphone and radio transmitter (Telemike) set at the position of the bat?s
ears and carried during flights to a landing point on a wall. Telemike
recordings confirm that flying horseshoe bats (Rhinolophus ferrumequinum
nippon) adjust the frequency of their sonar broadcasts to compensate for
echo Doppler shifts. Returning constant frequency echoes were maintained at
the bat?s reference frequency ±83 Hz during flight, indicating that the bats
compensated for frequency changes with an accuracy equivalent to that at
rest. The flying bats simultaneously compensate for increases in echo
amplitude as target range becomes shorter. Flying bats thus receive echoes
with both stabilized frequencies and stabilized amplitudes. Although it is
widely understood that Doppler-shift frequency compensation facilitates
detection of fluttering insects, approaches to a landing do not involve
fluttering objects. Combined frequency and amplitude compensation may
instead be for optimization of successive frequency modulated echoes for
target range estimation to control approach and landing.
URL: http://www.springerlink.com/content/v4q5p88510816317/
For reprints please contact Shizuko Hiryu (Email:
Kind regards
Sonja
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Dr. Sonja Amoser
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