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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 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