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Re: perception of circling horn



At 11:10 AM 4/20/00 -0500, Paul O. Johnson wrote:
I thought we localized sound only through the
slight differences in time of arrival and intensity at the two pinnae. Do
we
know the weighting our brains place on phase differences?

There are (at least) two methods of determining the location of the sound.

For low frequencies, timing differences are used. The crest of a wave will
reach one ear at a different time than it will reach the other. The closer
ear will obviously hear it first, by an amount depending on the location of
the source and the distance between the ears. Simultaneous arrival means
straight ahead (or behind).

However, at higher frequencies this doesn't work. Once the wavelength is
shorter than the distance between the ears, two crests could arrive
simltaneously but actually be (360)n degrees out of phase. So a sound from
the side would be erroneously judged as coming from straight ahead.

In this regeme, loudness differences are used. These high frequency sounds
don't diffract well, so the "shaded" ear will hear a much quieter sound.

I believe that essentially all location is done by phase difference at low
frequency and by intensity at high frequency, with a middle ground where
neither works well.



Tim Folkerts