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Re: 'pressure at the ears' visiting an anechoic chamber
At 03:29 AM 10/28/98 +0000, Jont Allen wrote:
>Dear List,
>I have been doing some "research" about this pressure
effect in the ears,
>when you enter the anechoic chamber (AC). I called Cyril Harris,
and asked
>him for his opinion on this effect. He had to think about it,
and didn't
>have an answer of the top of his head, but he came up with a
reasonable
>explanation, I think.
>
>When you have pressure on your ears, there is lots of static
(low frequency)
>pressure relative to high frequencies. He suggests that when you
walk into
>the AC, the high frequencies are damped, but not so much for the
lows.
>Thus the spectral balance is tilted heavily toward the low
frequencies.
>It is, he argues, the strong low frequency bias towards the low
end of
>the spectrum that gives the "pressure effect," just as
in the case of
>normal high frequencies with a static pressure.
>
>What do you think of this explanation?
>
>Jont Allen/Cyril Harris
>
The low-frequency dominance of the sensation may have to do with the
internal noise suddenly becoming unmasked by the ambient noise we are
used to live with in our non-anechoic and non-attenuated environment. You
can learn more about the spectrum of the internal noise, estimated via
some clever psychophysical experiments, in C.S. Watson, J.R. Franks &
D.C. Hood's 1975 JASA paper (v. 52) "Detection of tones in the
absence of external masking noise. I. Effects of signal intensity and
signal frequency". The paper may be old but, just as some of us, it
is steadily improving with age.
Pierre
****************************************************************************
Pierre Divenyi
Experimental
Audiology Research (151)
V.A. Medical Center, Martinez, CA 94553, USA
Phone: (925) 370-6745
Fax: (925) 228-5738
E-mail :
pdivenyi@marva4.ebire.org
****************************************************************************