Thread Subject: Re: Amplification and Research

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From: jagbell@nyc.rr.com
Date: Mon, Mar 26 2007 10:00 AM

Diane-

I beg to disagree with you on this issue.:) This is the whole premise behind Starkey's custom made hearing aids. :)
Please see my previous e-mail on my testing the ipod.

Best,

Janice
Sent from my BlackBerry wireless handheld.

-----Original Message-----
From: Diane Golden < = EMAIL ADDRESS REMOVED = >
Date: Mon, 26 Mar 2007 11:04:54
To:'TEITAC Telecommunications Subcommittee' < = EMAIL ADDRESS REMOVED = >
Subject: Re: [teitac-telecom] Amplification and Research

Paul wrote:

> I have absolutely no idea whether our measures of perceived quality would
correlate highly with intelligibility among
> listeners who are hard-of-hearing.

Jim wrote:
Yes, there needs to be research into mapping these metrics onto the domain
of hearing loss, either objectively or subjectively. But I can't believe
we'd be the first people asking for such a linkage.

>From Diane: Let my try a crack at this again -- first by saying that I am
an audiologist by training (still licensed and practice a bit on the side
periodically . . . ) If audiologists had some way to "solve" speech
intelligibility problems for folks with sensorineural hearing loss -- we'd
have a lot more people lined up to buy hearing aids. Audiologists pull out
every "trick in the book" from digital manipulation of the speech signal,
venting and open fittings, etc. etc. trying to improve speech discrimination
through hearing aid fitting. But for many individuals you still can't
improve discrimination to a decent level regardless of what signal
manipulation techniques are used. So there is no "metric" to be applied to
a speech signal delivered by a phone that will ensure intelligibility for
individuals with sensorineural hearing loss -- and in fact the technology
doesn't exist to deliver intelligibility to everyone with hearing loss.

With telephones, for people with really poor discrimination, we're forced to
shift to text (regular VCO or captioned VCO) to allow them to use the phone.
Many of these individuals can manage in face-to-face communication by using
speech reading cues; but since those are gone on the phone their speech only
discrimination is just too poor to deliver any reasonable level of
intelligibility. Just as a side note, we've found a good number of people
with poor discrimination, yet fairly good speeech reception thresholds
(maybe in the 50 dB HL range), are unable to use captioned VCO (with
combined text and speech) because the presence of the speech (audible but
unintelligible) interferes with their ability to use the captioning. These
individuals are able to use captioned VCO with the speech off or turned down
below their threshold, but not when both are received as incoming
information. Yet other individuals with a similar hearing loss
configuration and similar speech discrimination are able to use combined
speech/text. This is just another example of the individual differences
between people with hearing loss in how they process speech signals.

So in a nutshell it is critical to get the speech signal to the speech
threshold of a person with a hearing loss to have any chance of
intelligibility. Past that, to improve speech discrimination for
individuals with significant cochlear and/or retro-cochlear damage means
buildling telephones with all kinds of adjustable features (similar to what
high end hearing aids have available) and even at that there is no assurance
that discrimination can be delivered. (And I'm thinking is probably beyond
the scope of 508 and/or 255 standards.) Generally accepted practices like
reducing ambient noise would work across the board especially if user
controlled. Other user adjustable features like one to shift the frequency
response might be helpful but trying to require an adjustable frequency
response could be a challenge in a standard.

Diane

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