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Loudness decay

Eric Smith erc at cinenet.net
Sat Dec 2 05:33:31 EST 1995

In article <49isa9$m1k at usenetw1.news.prodigy.com>,
Michael Ridenhour <SZFF25C at prodigy.com> wrote:
>I would urge you to see an audiologist asap, or an otolaryngologist. Self 
>diagnosis, as well as internet diagnosis are dangerous things. The 
>symptoms you describe can be bilateral, although it is a rare phenomenon, 
>and are pretty much dead on for an acoustic neroma, which is a relatively 
>benign tumor, but it is located in the wrong place, inside the internal 
>auditory canal, which opens into the brain. There is very little excess 
>space here, so the tumor begins to displace the part of the brain closest 
>to it. Eventually, loss of hearing, balance, taste, facial sensation, and 
>death can result. It is very slow growing, however. You have several 
>years before really nasty symptoms appear.
>Or it could be something simple, and easily explained. My point is, YOU 
>Sorry for shouting, but from your question, I assume you are getting hard 
>of hearing already.

This is not a case of self-diagnosis, but rather of trying to get
additional input to discuss with an ENT who doesn't seem to have much
expertise in this area.  For example, an acoustic neuroma doesn't seem
to have occurred to him as a possibility.  If I ask him if it could be
an acoustic neuroma, that might get him thinking about it, such that he
might decide to do some more testing or whatever.

One indication that it's probably not an acoustic neuroma is that the
deafness has been progressive for decades.  But on the other hand, it
seems perfectly possible for a long-deafened person to get an acoustic
neuroma at any time.

I will of course take all internet advice with a grain of salt, but the
value of the advice is in suggestions of what to ask about, rather than
of what to conclude.

What I want now is more suggestions of other possibilities to ask
about.  To repeat the symptoms, steady tones seem to fade away
gradually till they are perceived as being completely gone, but when
the tone is then interrupted for a fraction of a second, it is
perceived as coming back at full loudness.  Also, before it has faded
away completely, it seems to change from a tone to a remote din.  In
other words, it doesn't fade to a faint tone before fading away, but
rather loses its tonal quality first.

Another symptom, which I may not have mentioned before, is that while
there is severe recruitment at low frequencies, it's just the opposite
at high frequencies.  In other words, when 30 dB is added to a high
frequency tone that sounded very faint at threshold, it still sounds
faint, as if only 5 or 6 dB were added.  When it's louder, it starts to
sound very slightly painful, but still doesn't have the loudness
quality of a loud and clear tone.  In other words, it seems faint but
still causes a small amount of the kind of pain that comes from hearing
a too-loud sound.

The fact that this deafness is bilateral and long-progressive indicate
that it's probably not caused by an acoustic neuroma, although that is
worth asking about.  But the real question right now is what else could
it be?  Only by knowing what it could be would I know what possibilities
to ask about.

Another thing I may have forgot to mention is that this deafness has
progressed to the point where all frequencies above 1500 have
thresholds at or above 100 dB.  So, for example, in the above mentioned
test, where 30 dB was added to threshold, I'm talking about adding 30
dB to 100 dB, with the resulting 130 dB tone still sounding faint, even
though it was 30 dB above threshold.  This test used some special test
equipment not normally found in an audiologist's office, so you might
suspect that the equipment itself is at fault.  However, that's not the
case, and similar results were obtained with hearing aids.  For
example, with hearing aids that output 138 dB at high frequencies, loud
high frequency tones still sound faint even though they are 30+ dB
above threshold.  If the loudness is increased gradually from threshold
to 30+ dB above threshold, the perception is of a much slower increase
in loudness, resulting in a total increase of maybe 5 or 6 dB.

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