Time-frequency model for echo-delay resolution in wideband biosonar.
A time/frequency model of the bat's auditory system was developed to examine the basis for the fine (approximately 2 micros) echo-delay resolution of big brown bats (Eptesicus fuscus), and its performance at resolving closely spaced FM sonar echoes in the bat's 20-100-kHz band at different signal-to-noise ratios was computed. The model uses parallel bandpass filters spaced over this band to generate envelopes that individually can have much lower bandwidth than the bat's ultrasonic sonar sounds and still achieve fine delay resolution. Because fine delay separations are inside the integration time of the model's filters (approximately 250-300 micros), resolving them means using interference patterns along the frequency dimension (spectral peaks and notches). The low bandwidth content of the filter outputs is suitable for relay of information to higher auditory areas that have intrinsically poor temporal response properties. If implemented in fully parallel analog-digital hardware, the model is computationally extremely efficient and would improve resolution in military and industrial sonar receivers.
Neretti
Nicola
N
Brain Sciences, Brown University, Providence, Rhode Island 02912, USA. nicola_neretti@brown.edu
Sanderson
Mark I
MI
Intrator
Nathan
N
Simmons
James A
JA
D000818:Animals; D001303:Auditory Cortex / Q000502:physiology; D001306:Auditory Pathways / Q000502:physiology*; D001933:Brain Stem / Q000502:physiology; D002685:Chiroptera / Q000502:physiology*; D003198:Computer Simulation; D004455:Echolocation / Q000502:physiology*; D008432:Mathematical Computing; D008636:Mesencephalon / Q000502:physiology; D009949:Orientation / Q000502:physiology; D010897:Pitch Discrimination / Q000502:physiology; D013018:Sound Spectrography