Re: [AUDITORY] National Hearing Test

I took the test just now and got the expected result: "slightly below normal range" in both ears (expected, based on previous tests that show somewhat worse than typical hearing for my 61-year age).

It would be great if there was better quantification of the result, like dB of SNR degradation relative to normal, rather than just "slightly below normal range". Charles, is there a numeric range associated with these words?

It does seem like a pretty effective test of hearing in noise. I presume it's doing an adaptive SNR process, since it would usually give me a relatively easy one after each one where I was pretty much guessing.

What I'd like to understand better is exactly how the mechanisms causing threshold elevation also cause degradation of SNR threshold. I presume that the auditory filter bandwidths are wider, and the compression less, with hearing loss. But they're also wider at high levels, and high levels don't cause a degraded SNR threshold, do they? Or maybe they do, in normal hearing, at levels high enough to cause this much bandwidth widening?

I've definitely been feeling a degraded ability to deal with conversation in noisy environments (cafes and such), which I understand is correlated with absolute threshold elevation. I'm just not clear on why it's so correlated. Is it understood? Is there a good paper on this?

Dick

On Wed, Oct 30, 2013 at 9:02 AM, Watson, Charles S. <watson@xxxxxxxxxxx> wrote:

Tom,
I know it is hard to accept that the telephone test works as well as it does, given the experiences we have all had with a range of signal qualities for unselected home telephones. However the data showed that tests taken with over 100 different home phones used by the veterans in our validation study yielded a similar correlation between the telephone SNR for 50% correct recognition and average pure-tone thresholds to that obtained with the carefully selected telephones used to administer the test in three VA clinics. We have also tested a sample of different phones to determine the range of distortion and bandwidths, and found them to be acceptable if speech heard over them was not noticeably distorted.

Most importantly, the range of absolute levels delivered by various phones would be quite important if the test measured pure-tone thresholds in the quiet. The test works because of the insight of Smits and his colleagues that SNR thresholds can be quite reliable under a range of reproductive conditions for which absolute thresholds would be virtually meaningless.

Chuck Watson

-----Original Message-----
From: Tom Brennan [mailto:g_brennantg@xxxxxxxxxxxxxxx]
Sent: Wednesday, October 30, 2013 6:01 AM
To: Watson, Charles S.
Cc: AUDITORY@xxxxxxxxxxxxxxx
Subject: Re: National Hearing Test

Actually, my comments about telephone service are based on having lived in Germany for nearly five years and having a number of friends in Europe. I do believe their telephone system superior to ours. This is especially true of their cell phone system but is to a lesser degree of their land lines.

I wonder if some kind of feedback loop could legally be set up to help know what kind of phone system a client doing this test i susing.

Of course, another issue revolves around the fact that most telephones now allow the user to control the volume of the receiver thus adding another confo7unding variable to the mix.

Tom

Tom Brennan KD5VIJ, CCC-A/SLP
web page http://titan.sfasu.edu/~g_brennantg/sonicpage.html