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Sonar gain control and echo detection thresholds in the echolocating bat, Eptesicus fuscus
J A Simmons1, A J Moffat, W M Masters
1Department of Psychology, Brown University, Providence, Rhode Island 02912.
The Journal of the Acoustical Society of America
|February 1, 1992
Summary
Echolocating bats adjust their hearing sensitivity to maintain a constant echo loudness, likely through middle-ear muscle contractions, aiding in target detection during flight.
Area of Science:
- Animal Behavior
- Bioacoustics
- Neuroethology
Background:
- Echolocating bats adjust auditory sensitivity based on echo delay.
- This adjustment is crucial for detecting sonar echoes accurately.
Purpose of the Study:
- To investigate the echo gain control mechanism in echolocating bats.
- To determine the role of middle-ear muscle contractions in this process.
Main Methods:
- Using an electronic target simulator to control echo delay.
- Testing the echolocation detection threshold of the bat (Eptesicus fuscus).
Main Results:
- Bat's detection threshold improved by 11.5 dB as echo delay increased from 2.3 to 4.6 ms.
- This suggests an echo gain control reducing sensitivity with increasing echo amplitude.
- The effect is comparable to forward masking, potentially mediated by middle-ear muscle contractions.
Conclusions:
- Echolocating bats exhibit an echo gain control mechanism.
- Middle-ear muscle contractions synchronized to vocalizations likely contribute significantly to this gain control.
- This mechanism helps maintain a constant sensation level for echoes during target approach.