Ear damage by hearing aid? - Yes, can happen
jay1000
theoretical but, unfortunately, are based on an extremely small data sample.
John Macrae in the journal of Speech and hearing Research, Volume 34,
403-414, April 1991 sums it up very concisely:
"Although there are as yet no generally accepted guidelines on the matter,
it seems likely that, for any particular degree of hearing loss, there is an
amount of amplification that is excessive and will result in deterioration
of the remaining hearing of the hearing aid user".
Most of the data for this article came from only 8 children with bilateral
hearing loss who were fitted with a single powerful body-worn aid, which
they cranked to the maximum volume setting of 6 instead of the mid-range
setting of 3 (the hooked-on-power syndrome). The excessive sound power did
cause a hearing loss but, as expected, only in the aided ear and not the
unaided. The kids had aids with average 1000 Hz gain of 60 dB and maximum
power output (MPO) of 126 dB. At the full-on volume control setting of 6
they would be exposed to 126 dB for a significant fraction of the day,
especially with the older linear aids with no compression. I assume the
aids did have peak-clipping.
Modern hearing aids can also have similar gains and MPO, but hopefully with
advanced compression or signal processing the output will be well below the
126 dB for most of the day. However, it is a tricky balance for a profound
loss. Output has to be high enough for speech discrimination benefits and
low enough to avoid hearing damage.
Bill M
them, jay1000 wrote:
"However, it is a tricky balance for a profound
loss. (snip) "
Something an audiologist can agonize over, I bet. Especially with kids!
Who would want to risk harming the hearing of a child that already has bad
hearing?
Who wouldn't want to make the most of the prime language learning years? So
many people never get a grasp on English or Spanish, and reading problems
result.
People who can't hear need literacy more than most, and it's too common that
language skill isn't developed.
Bill M
klunk
> I have read a couple of articles on the subject. They are highly
> theoretical but, unfortunately, are based on an extremely small data
sample.
Thanks for posting this information. This is a very important
yet neglected topic.
> Modern hearing aids can also have similar gains and MPO, but hopefully
with
> advanced compression or signal processing the output will be well below
the
> 126 dB for most of the day. However, it is a tricky balance for a
profound
> loss. Output has to be high enough for speech discrimination benefits and
> low enough to avoid hearing damage.
Actually, compression has the effect of RAISING the average
signal level. So I think it is very important with modern aids
to ensure the MPO is set as low as possible.
jay1000
"klunk" <sorr...@microsoft.com> wrote in message
news:1m6Uc.47470$Lj.1649@fed1read03...
That's an interesting observation and very true. MPO should be set as low
as possible.
However, even if a compression aid raises the average signal level does it
push the average signal level closer to the MPO? Is 115 plus or minus 5
better than 117 plus or minus 2? I'm not an audiologist but I thought that
with variable compression that it was harder to hit the MPO.
This also raises the question of what kind of average and what deviation is
significant as far as potential hearing loss. There are the mean, the mode
and the median averages. In addition there are various weighed and
geometric averages. I think some sort of non-linear weighted average with
an OSHA type noise limit as a weighting factor might be the most
significant.
As far as the Macrae data, I think that we also have to look at the output
level of a compression aid relative to the output level of a linear aid
pushed to maximum volume control output.
It's a very confusing topic and there obviously has not been sufficient
research or analysis.
tls...@concentric.net
took a very strange rock and inscribed these words:
>People who can't hear need literacy more than most, and it's too common that
>language skill isn't developed.
My opinion is that most hearing people take literacy too much for
granted and don't think it will be a problem, or don't value it to
begin with, so the resources get devoted to the more "obvious" problem
of ears that don't work.
I say build to your strengths, not to your weaknesses...this myopic
focus on the ears is ridiculous.
--
Therese Shellabarger / The Roving Reporter - Civis Mundi
tls...@concentric.net / http://tlshell.cnc.net/
HEARA1
>they cranked to the maximum volume
>it is a tricky balance for a profound
>loss. Output has to be high enough for speech discrimination benefits and
>low enough to avoid hearing damage.
>
A very good example of why it is MUCH more important to choose an Excellent
Experieced Provider than any particular brand!!!!!!