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Re: TTS as surrogate for noise exposure measurement

Hi Bob, list!

Just some thoughts from my side:

- TTS has (if evoked by not-so dangerous exposure) a rather short time constant - I think for levels around 80 dB (don't nail me down on that) that is below (some) 10 minutes. Everything above (evoking longer lasting TTS) might be slightly longer. I recall that 2 (?) years ago there was a study by Chris Plack on Night club sounds (presented at BSA)...maybe there you find some more reliable data re the time constants ion connection with music.

- Just measuring a pure-tone threshold might not be the best idea. Due to fine structure effects (e.g., work of Glenis Long et al.) you might misinterpret the result of there is a slight shift in FS due to whatever effect. FS is in general rather stable on the big picture, but for a pure tone I would not rely on the precision for a single point. If such an approach was taken, use either wobble-tones (with a frequency modulation, proposed by Zwicker) or narrowband noise.

[I would rather suggest to get rid of in-ear headphones and to limit the level to a "comfortable" loudness (maybe evaluated with some weirdo Modern-Talking song to get rid of preference effects). The fear of damaging the innear ear without being a chicken should be the best protection...]



On 15/04/13 15:02, Bob Masta wrote:
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

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.

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

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
Data AcQuisition And Real-Time Analysis
Scope, Spectrum, Spectrogram, Signal Generator
     Science with your sound card!

Bastian Epp
Assistant Professor
DTU Electrical Engineering
Technical University of Denmark
Department of Electrical Engineering
Ørsteds Plads
Building 352
2800 Kgs. Lyngby
Direct +45 45253953