Hyperacute directional hearing (Martin Braun )

Subject: Hyperacute directional hearing
From:    Martin Braun  <nombraun(at)POST.NETLINK.SE>
Date:    Sat, 7 Apr 2001 14:40:24 +0200

Dear all, The latest news in the abstract below may be of interest to many list members, because it is relevant for both biology and engineering. What do our experts on directional hearing think of this? ______________________________________________________________ Hyperacute directional hearing in a microscale auditory system ANDREW C. MASON, MICHAEL L. OSHINSKY & RON R. HOY Nature 410, 686 - 690 (2001) Abstract: The physics of sound propagation imposes fundamental constraints on sound localization: for a given frequency, the smaller the receiver, the smalle= r the available cues. Thus, the creation of nanoscale acoustic microphones with directional sensitivity is very difficult. The fly Ormia ochracea possesses an unusual 'ear' that largely overcomes these physical constraints; attempts to exploit principles derived from O. ochracea for improved hearing aids are now in progress. Here we report that O. ochrace= a can behaviourally localize a salient sound source with a precision equal = to that of humans. Despite its small size and minuscule interaural cues, the fly localizes sound sources to within 2=B0 azimuth. As the fly's eardrums= are less than 0.5 mm apart, localization cues are around 50 ns. Directional information is represented in the auditory system by the relative timing = of receptor responses in the two ears. Low-jitter, phasic receptor responses are pooled to achieve hyperacute timecoding. These results demonstrate th= at nanoscale/microscale directional microphones patterned after O. ochracea have the potential for highly accurate directional sensitivity, independe= nt of their size. Notably, in the fly itself this performance is dependent o= n a newly discovered set of specific coding strategies employed by the nervou= s system. _______________________________________________________________ Martin Braun Neuroscience of Music Gansbyn 14 S-671 95 Kl=E4ssbol Sweden nombraun(at)post.netlink.se

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Electrical Engineering Dept., Columbia University