On-board telemetry of emitted sounds from free-flying bats: compensation for velocity and distance stabilizes echo frequency and amplitude.
Level 5 - mechanism / opinion, no new human data
Level 5 by clinical CEBM criteria (animal neuroethology experiment).
PubMed 18663454 · doi:10.1007/s00359-008-0355-x
What was done
Researchers recorded echolocation broadcasts and returning echoes from free-flying horseshoe bats (*Rhinolophus ferrumequinum nippon*) approaching a wall landing point. Recordings were obtained using an on-board miniature microphone and radio transmitter ("Telemike") placed near the bats' ears.
What was found
Flying bats adjusted their emission frequencies to counter Doppler shifts, holding returning constant-frequency echoes at the reference frequency ±83 Hz (matching resting accuracy). Simultaneously, bats reduced broadcast power as target range closed to compensate for distance-dependent amplitude gains, resulting in stabilized echo frequency and amplitude. The abstract provides no other numerical values.
Why it matters
By directly recording the auditory input received at the bat's ears during flight, this study demonstrates that dual frequency and amplitude stabilization occurs during stationary landing approaches, indicating a role in precise target range estimation rather than solely fluttering insect detection.
Limits
The abstract does not disclose the sample size (number of bats or flight trials). The findings are restricted to a single species in a structured landing task and may not generalize to other echolocating species or complex natural foraging environments.
Cited by
- supports Constant-frequency echolocating bats dynamically adjust their vocalization frequencies in flight to compensate for Doppler shift so returning echoes remain in their acoustic fovea frequency range.