The recent practice of leaving user volume controls off
of hearing aids has presented new challenges for the
hearing impaired. Reader inquiries may be directed to
digicarenet@aol.com or by faxing to (719)676-6882.
Another Elephant in the Living Room: To VC or not to VC
by Max Stanley Chartrand, M.A.,
DigiCare Hearing Research & Rehabiliation
It was with great interest that I read the MarkeTrack VI
follow-up paper (“Isolating the Impact of the Volume
Control on Customer Satisfaction”, HR, Jan., 2003). It
was an admirable and scholarly effort to bring to the
surface an issue that has been somewhat suppressed as we
stretch toward the Utopian Age in amplification.
Obviously, those of us in the research and education end
of the field have fallen asleep at the wheel on this
one. The neglect in retaining the rightful and needed
place of the lowly volume control in the dispensing
regime, in my opinion, is much like the proverbial
elephant in the living room: so obvious that although we
keep stubbing toes, we fail to see the immensity of the
oversight.
By nearly all accounts in the literature relative to
whether a user volume control is an “option” or a
“necessity”, it has been presupposed that the defective
hearing system is a static not dynamic and changing
entity, or that one’s threshold actually remains
constant from day to day, from morning to night.
It is not constant.1 In fact, we’re not as tall at night
as we are in the morning (losing about ½” to 1”), nor is
our vision as acute, or any other sense, for that
matter. Even a normal hearing individual experiences an
end-of-day auditory fatigue loss of hearing sensitivity
of at least 1 jnd (3-4dB @1KHz). In the case of the
hearing impaired person with severe recruitment, that
single jnd can represent several jnds. And, of course,
AGC and WDRC have nothing to do with maintaining one’s
MCL throughout the day or even from day to day.
Moreover, if we were to program the gain of a VC-less
patient in the morning, by nightfall our patient will
complain of “dullness” (need for more gain), “fullness”
(own voice occlusion), or “not loud enough”2. So, let’s
say we instead program the VC in the evening, by next
morning the birds will be chirping a lot louder than
their liking. Back and forth we go, striving mightily to
avoid the one thing (user VC) by which the patient can
make real time accommodations as needed, until finally,
they complain, “But you told me these hearing aids were
automatic.” Well, yes, they do adjust external inputs
automatically---they just can’t control cochlear
microphonics.3
There’s good reason why Surr et al4 found that 77% of
experienced users prefer a VC, no matter how
sophisticated the “automatic” technology. There is also
good reason why returned hearing instruments without
VCs, as a proportion, far outnumber returned instruments
with VCs at the factory. Here are just a few more
ignore-at-our-peril reasons why user VCs should be the
rule not the exception:
§ Variations in Eustachian tube (dys)function (allergy,
colds, barometric and temperature changes, etc.)5
§ Auditory adaptation, suppression, fatigue, and
overload, common among hearing aid users.1,3
§ Fluctuating thresholds as a result of Meniere’s or
dietary ototoxicity.6
§ Limbic influences in the auditory experience (i.e.,
aversive conditioned reflexes).7
§ Variations in telephone outputs, hard-wire vs cellular
systems.8
§ MCL vs PB-Max levels in critical listening
situations.9
§ Abnormal loudness growth and loudness intolerance that
exceed WDRC or AGC limits.8
In light of the above and more, then, it is most
distressing today to see that many manufacturers’ order
forms are designed to promote instruments without a user
VC, causing dispensing professionals to go out of their
way to order instruments with VCs. Arguably this has
contributed to persistent returns for credit in the
digital and hybrid technology models8. It has also
negated an essential auditory rehabilitation tool away
from both patients and their hearing health
professionals.10 Of course, there are the 5-8% that
cannot handle a user vc, and for whom a number of
trade-offs must be made to meet the dexterity
limitation.
When uninformed prospective users are asked if they
would like to do away with the user VC, the answer most
often will be affirmative. But, then, if asked if they’d
like to dispense with wearing hearing aids altogether,
the answer would likely still be in the affirmative. The
burden of such a question on those not informed sets far
too many up for failure when they discover AGC and WDRC
are not as “automatic” as they were led to believe.
The elephant in the living room. Looming large,
stoically sitting there between today’s technological
achievements and the market desperately in need of it.
Dispensing professionals need to make user VCs the rule,
not the exception, and teach patients how to utilize
this most needed rehabilitative tool. Factory order
forms should reflect the use of a VC as the default
option configuration, not the other way around.
And, most important of all, our entire industry needs to
re-educate itself about the dynamicism of the human
hearing system, especially as it presents in the
defective ear. Hearing impaired patients will love us
for it, though they may not understand all the reasons
why.
References:
1. Willott, J.F., Aging and the Auditory System:
Anatomy, Physiology, and Psychophysics, San Diego:
Singular Publishing Group, Inc., pp. 168-201 (1991)
2. Chartrand, M.S., “In Vigorous Defense of Volume
Control”, Livonia, MI: The Hearing Professional, pp.
9-11, May-June, (2001).
3. Durrant, J.D., and Lovrinic, J.H., Bases of Hearing
Science, 2dn edition, Baltimore: Williams & Wilkins, pp.
248-250 (1984).
4. Surr, R.K., Cord, M.T., Walden, B.E., “Response of
hearing aid wearers to the absence of a user-operated
volume control”, Hearing Journal, 54(4):32-36.
5. Feldman, A.S., “Acoutsic Impendence-Admittance
Battery”, in Handbook of Clinical Audiology, 2nd
edition, ed., Katz, J., Baltimore: Williams & Wilkens,
pp. 356-374 (1981).
6. Chartrand, M.S., “Video Otoscopy Observation &
Referral: The FDA Red Flags”, Hearing Professional,
Jan.-Feb. (2003).
7. Hazell, J.W.P., “The TRT Method in Practice”, VI
International Tinnitus Seminar, London: Ed Hazell
Publications THC, pp. 92-98 (1999)
8. Chartrand, M.S., and Chartrand, G.A., The Nuts &
Bolts in Solving Problem Fitting Cases, a 12-hour
continuing education course, Livonia, MI: International
Institute for Hearing Instruments Studies, (2002).
9. Sandlin, R.E. “Principles of Sound Field Audiometry”,
in Hearing Instrument Science and Fitting Practices, 2nd
Edition, ed., Sandlin, R.E., Livonia, MI: International
Institute for Hearing Instruments Studies, pp. 615-618,
(1996).
10. Chartrand, M.S., Hearing Instrument Counseling:
Practical Applications in Counseling the Hearing
Impaired, Livonia, MI: International Institute for
Hearing Instruments Studies, pp. , (1999). |
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