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Loudness, Hearing loss, thresholds ...

I'm sorry that I can't frame this question quite correctly, but any help
would be useful.

My understanding is that in a 'hearing test' (just for freq response), a
series of tones of lower and lower amplitude are played until the subject
no longer perceives them (they are below the person's threshhold of hearing).

Given an 'A weighted' loudness curve:

if at the age of 15, my threshold at 1kHz was 10 dB, and for 100 Hz was 45
dB (standard (?) loudness response, the 10 phon curve);

when I am tested at age 50, and my 1 kHz threshold in 20dB, and my 100 Hz
threshold is 72 dB; (the curve indicates that the 20 phon threshold
should be 52 dB);

it would seem to indicate that I have had a 20dB (or 20 phon?) hearing loss
at 100Hz, as the normalized loudness curve would indicate that a 20 phon
loudness curve should have a 100 Hz threshold of 52 dB.

If I am monitoring a 90dB signal (at 1 kHz) will I perceive the 100 Hz
signal as being 20 db quieter than it would have been without the hearing
loss, or will I perceive it as being 12 dB lower in amplitude (based
upon the 70 phon curve).

This question arises as I would like to know if (while monitoring a
signal at 90dB), I should add 12, or 20 dB of 100Hz boost to 'hear it the
way others will'. My instinct says that being psychometric, equalization
should be determined by the phon (loudness) curves (but I'm not scientist).

Sorry not to be clear, but more and more frequently (younger) students in
sound classes are coming in with varying kinds and degrees of hearing
loss (notably at 4kHz), and 'equalization' issues come up.




      Professor K Austin
      EuCuE - Department of Music / Departement de musique
      universite Concordia University
      7141, rue Sherbrooke o
      Montreal, QC  H4B 1R6


tel: (1) 514 - 848 - 4709
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