Subject: Re: Selective numbing (was: Re: Why is high high?) From: Andrew Vermiglio <avermiglio(at)HEI.ORG> Date: Fri, 28 Aug 1998 11:17:18 -0700Eliot 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? My thought is that the numbing effect is a protective adaptation, which fails to come into play with loud bass sounds with a rich spectrum, such as is normally found in rock music, which, I think, does cause hearing loss. I don't go to rock concerts regularly but when I have I've never noticed the special selective numbing effect found in the other music. Eliot, if I am understanding you correctly, the "selective numbing" is also called a temporary threshold shift. Basically this means that the softest sounds that you could hear before the noise exposure have become inaudible. If your ability to hear these soft sounds is not restored then it is called a permanent threshold shift. Please note that this is not a protective adaptation. It is an indication of auditory system damage. High levels of sound exposure can result in damage to the cochlea. This damage may be perceived in two ways; 1) a hearing threshold shift and 2) a decreased ability to understand speech in noisy environments such as a crowded restaurant. There are several articles and books which cover this topic. You may want to look under the general topic of hearing conservation. Additionally, if you notice a change in your hearing you should be tested by an audiologist. Regards, Andy Vermiglio McGill is running a new version of LISTSERV (1.8c on Windows NT). Information is available on the WEB at http://www.mcgill.ca/cc/listserv