Re: Selective numbing ("Regis Rossi A. Faria" )

Subject: Re: Selective numbing
From:    "Regis Rossi A. Faria"  <regis(at)LSI.USP.BR>
Date:    Fri, 28 Aug 1998 15:19:06 -0300

Eliot Handelman wrote: > > Andy, during and after exposure to high-intensity high sounds > my frequency response was noticably numbed. My own voice souded > different to me afterwards, as though my hearing had been selectively anesthetized, > though after a few minutes things returned to > normal. I wonder whether anyone here knows of relevant studies > involving selected numbing of this sort? Although I don't have knowledge of formal studies on this (neither articles) maybe I can add some more flavour to the discussion presenting an effect I've been experiencing when exposed for some minutes to "buzzing" noises due to poor shielded microphones cables (bad ground or bad shield). After hearing this kind of noise for over 5 minutes (not loud, close in intensity to a normal human conversation) and turned off the mic (so stopping the noise) I noticed that all human voices I heard for some time were kind of "flangered", even my voice sounded as if flanger effect were being applied. It seems the noise had biased the hearing hardware so that incoming voice were just analysed with a different bias and producing a flanger effect. I didn't analyse the noise signal, but I suspect it is probably very rich in 60Hz (the AC power supply frequency). I go to Rock concerts every so often, and sometimes to night clubs with terrible agressive bass sounds and painful tweeters, and I have never noticed a flanger effect after exposure to these acoustic poluted environments. The effect was new to me. Concerning protective adaptations, I am sure that fine, constant and "well behaved" buzz that we hear after a rock concert or noisy night clubs is a result from a protective procedure the hearing hardware uses, that takes place even at the middle ear (the little bones change their impedance when loud sounds are present) and/or at the cochlear membrane and hair cells (which would change how some frequency bands are analysed or masked). Regis McGill is running a new version of LISTSERV (1.8c on Windows NT). Information is available on the WEB at

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