TTS as surrogate for noise exposure measurement (Bob Masta )

Subject: TTS as surrogate for noise exposure measurement
From:    Bob Masta  <audio@xxxxxxxx>
Date:    Mon, 15 Apr 2013 09:02:03 -0400

I've been contacted by a young person in Hungary who is concerened that his music listening habits may be damaging his hearing. He saw that my Daqarta software has a built- in SPL meter feature, and he wanted to know how to use it to measure the headphone level of his music, so he could keep it under 80 dB SPL. Unfortunately, he says he can't afford a calibrated microphone, which would of course be needed for any SPL measurements. Since this is just for "casual" purposes, not research, etc, he'd probably be happy with some sort of rule-of-thumb metric... but I don't know of any. I'm thinking here of non-technical things like they recommend for aerobic exercise, such as "walk fast enough so that you can just barely carry on a conversation"... only for hearing. (Anyone?) One problem is that I can't think of any household sounds with a standard loudness. Another is that if he already has some PTS he would get false assurance that his listening levels were not too loud. So my question for the group is about using TTS. The beauty of this is that it requires no absolute calibration. He could measure his threshold at some specified frequency in the morning before he starts his music listening, and record the level in dB relative to full scale (whatever it might actually be), then repeat it after listening and take the difference. He can use Daqarta to do this for free. I think if he finds *any* shift it means his music is too loud, but the converse is probably not true... especially if there is already some PTS, which would presumably reduce the amount of TTS. True? Any thoughts on this whole approach? I have discarded one possible alternative approach, which would be to listen at his usual level, then reduce the level until he can just barely hear it and record how much reduction that took. The problem with this dB-above- threshold measurement is once again that if there is PTS his higher threshold would make his music measure softer. Any other ideas? Thanks, and best regards, Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

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