Hyperacute directional hearing

[Martin Braun <nombraun@xxxxxxxxxxxxxxx>]

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?

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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 smaller
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. ochracea
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° 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 that
nanoscale/microscale directional microphones patterned after O. ochracea
have the potential for highly accurate directional sensitivity, independent
of their size. Notably, in the fly itself this performance is dependent on a
newly discovered set of specific coding strategies employed by the nervous
system.
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Martin Braun


Neuroscience of Music
Gansbyn 14
S-671 95 Klässbol
Sweden
nombraun@post.netlink.se