Your questions are, as usual, 'spot on' and in tune with my way of
While there is evidence (some of it highlighted by Pierre and
Bill) of degraded performance at high levels for normal hearing
listeners, I would argue that the degradation is comparatively
less for normal-hearing listeners than for hearing-impaired
listeners, even though as you said normal-hearing and
hearing-impaired listeners share common cochlear mechanical
properties at high levels. Also, a paper just published (Gregan et
al. 2013 JASA) suggests little correlation between residual
compression and masking release. Therefore, I think that reduced
compression and broader filters can explain only a (small) part of
the difficulty experienced by hearing-impaired at understanding
speech in noise. The question is what explains the other (larger)
part. I think the answer is 'deafferentation'.
We know that age is a separate contributor to degraded performance
in noise that adds on to hearing impairment. This is beautifully
shown by Table I of Peters et al. (1998, JASA 103:577-587). What I
find most interesting, however, is that age leads to auditory
nerve deafferentation (Makary et al. 2011, JARO) and
deafferentation also occurs after noise exposure (see Kujawa and
Liberman 2009) even in clinically-normal individuals. Therefore,
it is very likely that deafferentation occurs even more frequently
and significantly for hearing-impaired individuals. We have
recently shown (Lopez-Poveda and Barrios 2013 Front. Neurosci.)
that degradation of the acoustic signal inspired by
deafferentation can impair speech intelligibility in noise but
much less so in quiet without altering audiometric thresholds.
Altogether, this makes me think that deafferentation is a common,
underlying cause of degraded peformance in noise for both
hearing-impaired listeners and (audiometrically-normal) aged
listeners. What is more, I would dare saying that deafferentation
degrades performance in noise more than does reduced frequency
selectivity (broader filters) and/or reduced compression. The
mechanism of how deafferentation would degrade performance in
noise is described in our paper (Lopez-Poveda and Barrios 2013
That's my current thinking, anyhow, and here are some relevant
El 04/11/2013 21:13, Bill Woods escribió:
of your questions is easy to answer. Even listeners with
normal hearing show decreased intelligibility at constant
SNR as overall level is raised. Fletcher and his group saw
this in their work, and Studebaker et al. (1999) provide a
more recent set of data on this. I’ve seen different
arguments for why this might be the case but I’m not sure
it’s completely understood. Arguments would include
processes such as changing filter bandwidth, changing
compression amounts, and changing saturation of nerve fibers
as level is changed. (Judy Dubno’s group has also been
looking at this more recently.)
Pierre mentioned in an earlier post, Judy Dubno and Larry
Humes have done a great deal of work in the area of
understanding speech performance with aging and hearing
loss, and they have a very nice review chapter in a 2010
Springer book, “The Aging Auditory System”. I’d say their
chapter is a great place to start if you want to get a good
overview of the current state.
main issue Dubno and Humes (2010) point out is that basic
audibility accounting (using articulation index) goes a long
way in capturing a large portion of the variance of speech
performance across listeners. From this perspective, one way
in which the phone test results may yield correlation with
absolute thresholds is if the noise used is not above
absolute threshold in some important speech frequency region
(I assume the noise level is constant and the speech level
is adapted in the phone test, as in the Dutch version). When
this is the case, absolute threshold itself, and not the
noise, will be contributing to the speech level required for
50% correct, thus increasing correlation with pure tone
average (PTA) directly.
alone doesn’t always capture all the variance, however, and
there is ongoing research looking to understand the
influence of other contributors, such as reduced inner hair
cell and/or auditory nerve fiber count, which may manifest
as poor performance on basic, supra-threshold auditory tasks
such as frequency modulation detection (see, e.g., Strelcyk
and Dau, 2009). Note that these other contributors may
affect speech performance in quiet as well as in noise (see,
e.g., our 2013 paper on a related issue).
the end, the health of many of the processes contributing to
speech intelligibility performance in quiet and in noise may
all be correlated with age to some degree, and thus also
correlated with each other. It would be interesting to hear
from the Phone Test folks how much variance in predicted PTA
is reduced (or how much categorization into their three
categories is improved) when the phone test results are
added to predictions based on age alone.
Hearing Research Center
L. E., and Dubno, J. R. (2010). “Factors affecting speech
understanding in older adults,” in
The Aging Auditory System, edited by S.
Gordon-Salant, R. D. Frisina, A. N. Popper, and R. R. Fay
(Springer, New York), pp. 211–257.
O., and Dau, T. (2009). “Relations between frequency
selectivity, temporal fine-structure processing, and speech
reception in impaired hearing,” J. Acoust. Soc. Am. 125,
G. A., Sherbecoe, R. L., McDaniel, D. M., and Gwaltney, C.
A. (1999). “Monosyllabic word recognition at
higher-than-normal speech and noise levels,” J. Acoust. Soc.
Am. 105, 2431–2444.
W., Kalluri S., Pentony S., and Nooraei, N. (2013).
“Predicting the effect of hearing loss and audibility on
amplified speech reception in a multi-talker listening
scenario,” J. Acoust. Soc. Am. 133, 4268–4278.
AUDITORY - Research in Auditory Perception
On Behalf Of Richard F. Lyon
Sent: Thursday, October 31, 2013 11:21 AM
Subject: Re: National Hearing Test
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).
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?
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.
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?
On Wed, Oct 30, 2013 at 9:02 AM,
Watson, Charles S. <watson@xxxxxxxxxxx>
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.
Wednesday, October 30, 2013 6:01 AM
To: Watson, Charles S.
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
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 Brennan KD5VIJ, CCC-A/SLP
Enrique A. Lopez-Poveda, Ph.D.
Instituto de Neurociencias de Castilla y León
Departamento de Cirugía, Facultad de Medicina
Instituto de Investigación Biomédica de Salamanca
Universidad de Salamanca
Calle Pintor Fernando Gallego 1, 37007 Salamanca, Spain
Phone: (+34)923294500 ext. 1957. Fax: (+34)923294750