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High Frequency Hearing Aid

Phil McCandless pmccand at intop.net
Sat Jul 10 13:53:47 EST 1999


Jeff,

    High frequency hearing losses such as this one is difficult to fit.  I
have to say that I really like Dennis Van Vliet's response the best.

For years, audiologists have contemplated the technical impossibilities and
hopeful solutions to such dramatic losses. I sure hope that we find a
solution to the problem regardless of patient motivation.... But while we
argue for the best solution, let us not outsmart ourselves in the process...
Could it be that the 70 to 90 dB responses are test artifact?  Could it be
that this patient has NO measureable hearing above 3kHz?  While the
audiogram shows 70 to 90 dB "response", could this "response" be from some
other source?  Think about it....the real answer might suprise you...

In fact, it is more likely that this patient is responding to amplifier
noise or "hiss" rather than to tonal sensations.  Consider that the signal
to noise ratio on the BEST high-fidelity amplifiers is anywhere from 90 to
120dB.  The cochlear high frequency hearing loss such as the one you
described can be thought of as a physiologic low-pass filter with high-order
precision.  This means that the ear remains sensitive to low frequency
signals and would easily hear the hiss from even the best amplifiers if the
dial is set sufficiently high.   Low frequency hiss becomes audible at dial
settings of about 70 to 90 dB in the audiometers I have tested...

The way you can tell the difference in a patient with a precipitous hearing
loss and normal hearing in the lows is to simply ask the patient if he/she
hears a tone or a "hiss".  The answers might suprise you.  With losses like
this, I typically find that the patient reports a "hiss" around 70-80 dB,
but the sound *may* become audible as a tone if the dial is raised just a
few dB higher.  I consider tonal reports as the true threshold.   I report
hiss reports on the audiogram as "X and O responses" but I put the words,
"atonal" next to the audiometric responses if the report is only a "hiss".

Phil McCandless, Ph.D.


-----Original Message-----
From: Jeffrey Sirianni <audioman at hctc.net>
To: ASHA Listserve <asha-aud-forum at postman.com>; bionet.audiology
<audiolog at net.bio.net>
Date: Wednesday, July 07, 1999 12:07 AM
Subject: High Frequency Hearing Aid


>I saw a patient today with severe high frequency hearing loss, but normal
>through low and middle frequencies (250-2000 Hz = 5-15 dB HL; 3000 Hz and
>above 70-90 dB HL).  Most cases like this (that I have seen) do not really
>want hearing aids and I've struggled with those having minimum motivation
>with such a loss.  This patient seen today is motivated to hear better in
>noise and I think he would do well with a high frequency emphasis BTE,
>although picking out there is fairly slim.  Can anyone suggest a
>manufacturer & model that has worked well for such a patient.
>
>Thanks,
>
>Jeff
>
>
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