Noise interference with echo delay discrimination in bat biosonar

作者：Simmons J A^*

来源：Journal of the Acoustical Society of America, 2017, 142(5): 2942-2952.

DOI：10.1121/1.5010159

Echolocating big brown bats (Eptesicus fuscus) were trained in a two-choice task to discriminate differences in the delay of electronic echoes at 1.7 ms delay (30 cm simulated range). Difference thresholds (similar to 45 mu s) were comparable to previously published results. At selected above-threshold differences (116 and 232 mu s delay), performance was measured in the presence of wideband random noise at increasing amplitudes in 10-dB steps to determine the noise level that prevented discrimination. Performance eventually failed, but the bats increased the amplitude and duration of their broadcasts to compensate for increasing noise, which allowed performance to persist at noise levels about 25 dB higher than without compensation. In the 232-mu s delay discrimination condition, echo signal-to-noise ratio (2E/N-0) was 8-10 dB at the noise level that depressed performance to chance. Predicted echo-delay accuracy using big brown bat signals follows the Cramer-Rao bound for signal-to-noise ratios above 15 dB, but worsens below 15 dB due to side-peak ambiguity. At 2E/N-0 = 7-10 dB, predicted Cramer-Rao delay accuracy would be about 1 mu s; considering side-peak ambiguity it would be about 200-300 mu s. The bats' 232 mu s performance reflects the intrusion of side-peak ambiguity into delay accuracy at low signal-to-noise ratios.

• 出版日期2017-11