Abstract
An echolocating bat produces echoes consisting of the convolution of echolocation call and the impulse response (IR) of the ensonified object. A crucial question in animal sonar is whether bats are able to extract this IR from the echo. The bat inner ear generates a frequency representation of call and echo and IR extraction in the frequency domain requires accurate analysis of both magnitude and phase information. Previous studies investigating the phase sensitivity of bats using a jitter paradigm reported a temporal acuity down to 10 ns, suggesting perfect sonar phase representation. In a phantom-target playback experiment, we investigate the perceptual phase sensitivity of the bat Phyllostomus discolor using a novel approach: instead of manipulating IR phase by changing IR delay (jitter paradigm), we randomized IR phase and thus lengthened the IR over time, leaving the magnitude spectrum unchanged. Our results show that phase sensitivity, as reflected in the analysis of signal duration, appears to be much lower than phase sensitivity, as reflected in the analysis of signal onset. The current data indicate that different temporal aspects of sonar processing are encoded with very different temporal resolution and thus an overall claim of “phase sensitivity” as such cannot be maintained.
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Abbreviations
- DAP:
-
Data acquisition processor
- FIR:
-
Finite impulse response
- IR:
-
Impulse response
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Acknowledgments
We thank Uwe Firzlaff, Nicholas A. Lesica and Kiri Couchman for helpful comments on earlier versions of this manuscript. We also thank Christian Leibold for help in the reconstruction of the phase-shifted IRs. The experiments reported here comply with the “Principles of animal care”, publication No. 86-23, revised 1985 of the National Institute of Health, and also with the current German laws. This work was supported by the “Deutsche Forschungsgemeinschaft”, Wi 1518/7 (to L.W.).
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Schörnich, S., Wiegrebe, L. Phase sensitivity in bat sonar revisited. J Comp Physiol A 194, 61–67 (2008). https://doi.org/10.1007/s00359-007-0290-2
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DOI: https://doi.org/10.1007/s00359-007-0290-2