TTS as surrogate for noise exposure measurement

[Bob Masta <audio@xxxxxxxxxxx>]

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
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