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TTS related to PTS?

Michael Forrest michael_forrest at lineone.net
Sun Jan 30 18:41:21 EST 2000

"WILLIAM STOBIE" <9657701 at mull.sms.ed.ac.uk> wrote in article
<86kh5h$dq7$1 at mercury.hgmp.mrc.ac.uk>...
> Is there any hard evidence for a link between Temporary Threshold 
> Shift and Permanent Threshold Shift in hearing levels.  Can the former 
> be used to predicty the latter?
> Thanks a lot for any help
> 9657701 at sms.ed.ac.uk
AIUI the whole topic goes back a very long way. The 1965 CHABA criterion
(don't bother to remember this one, well out-dated) used TTS as an
indicator of damage based on an observation the TTS was approximately
numerically equal to eventual PTS for exposures repeated over a working
lifetime (IIRC). However the point was very clearly made that this applied
ONLY for average losses in large groups of people NOT for individuals. The
point of TTS is that it could be induced in controlled conditions, without
having to rely on epidemiological evidence of PTS, which in some cases is
of poor quality or unavailable. 
Back in those days, some very large TTSs were induced experimentally and
could take quite a time to recover. I can't imagine anyone doing that now. 
The mechanism of TTS isn't altogether clear. 

Regards, Mike

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