Premium Digital Hearing Aids - By Mark Ross, Ph.D.

This article first appeared in the March/April issue of Hearing Loss
magazine, a publication of HLAA, Hearing Loss Association of America
http://www.hearingloss.org/

Republished with permission of the author.
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Premium Digital Hearing Aids

Mark Ross

A “premium” or “top of the line” hearing aid is one that incorporates the
most technologically advanced and potentially useful features currently
available. One recent trade journal article defines the difference between a
premium hearing aid and other models as the inclusion of automatic and
innovative features. The more of these that are included in a given aid, the
greater the likelihood that it would be considered a premium or top of the
line model. Clearly, the designation also carries with it the implicit, if
not explicit, promise that the overall benefits that one achieves with a
premium hearing aid are going to exceed those obtainable with a more
economical hearing aid. But we should keep in mind that it is also a hearing
aid that invariably comes with a price tag commensurate with the elite
label.

According to the article, the determining consideration in moving from an
entry level (less expensive) hearing aid to a premium (more expensive) model
is the user’s life style, that is, whether he or she leads a busy, active
life in many different listening environments, or whether social time is
spent in quiet, less demanding listening environments. We should note that
the ability to actually hear better with these aids is not mentioned in the
article. Convenience is stressed and not hearing. The reason for this, I
suspect, is that there is little or no clinical evidence that directly
compares the hearing performance of premium aids with other hearing aids.

The final factor in recommending a premium hearing aid for a particular
person is, again according to the above-mentioned article, based on
budgetary constraints. No matter what a person’s life-style, a premium
hearing aid should be recommended only for those who can afford to pay the
“premium” price. Thus, the intention is to try to meet a person’s listening
needs within the very real limits of affordability. A premium hearing aid,
therefore, would be reserved for those who have an active life, are socially
active, and can afford to pay a “premium” price for the added convenience of
the special features.

In our society, we are conditioned to believe that “you get what you pay
for.” We are accustomed to quality differences being reflected in the cost
of an object or service. The notion that this also applies to hearing aids
does not seem strange to us. If someone has listening needs that require
the inclusion of the latest automatic and innovative features, and can
afford the premium cost, why shouldn’t this person purchase what he or she
desires (and presumably needs)? While one can, perhaps, make a social
policy argument against this notion, a more telling reason is that the
presumed listening benefits of a premium hearing aid have little or no
support in the hearing aid literature. In other words, the idea that people
are getting extra hearing benefit commensurate with the additional cost is
debatable. Evidently many people who purchase premium hearing aids feel the
same way, since industry figures show that fully 26% of such aids are
returned for credit.

In recent years, the sheer number of new features introduced in digital
hearing aids has been enormous. The various hearing aid companies are in a
constant and intense competitive race to introduce new ones in order to
differentiate themselves from their competitors. Different hearing aid
models, incorporating what is presented as some “revolutionary” new
development, seems to be introduced every year or so. Capturing or
maintaining market share – the economic imperative – is clearly the driving
force. In the ideal world, no new hearing aid feature would be introduced
until and unless its presumed listening benefits were evaluated and
substantiated with human beings. But from what I can see, this does not
happen very often. Instead of evidence of the clinical benefit of some newly
introduced feature, what we get is promotional material presented as
self-evidently positive. (I mean, who can argue with hearing aids that
employ “artificial intelligence,” nano-technology, or include a 128-channel
adaptive noise reduction circuit?) It is difficult for anyone, consumer or
professional, not to be impressed when reading this material – I know that I
am. It all sounds so logical – but we do have to keep in mind that a
marketing description, no matter how appealing or self-evidently obvious, is
not equivalent to a well-controlled clinical (not laboratory) research
study.

As a consequence of the rapid introduction of new hearing aid models, it
seems that the features highlighted in a previous generation of premium
hearing aids are now being included in this year’s “entry level” or
“affordable” models. The features haven’t changed; the presumed advantages
of last year’s model are still as relevant (or irrelevant) as ever. . We
can get some idea of what constituted a previous generation’s “premium”
hearing aid by looking at a table in the article cited above in which the
characteristics of 25 “affordable” hearing aids are briefly described. Some
of the more common features included with these currently- labeled
affordable hearing aids are:

· Wide Dynamic Range Compression (WDRC). This feature automatically
varies the amount of amplification applied to an input sound signal. Soft
sounds may be amplified somewhat more then louder sounds, with the intention
of making them audible, but still soft. Loud input sounds will receive less
amplification, but should still sound loud, although not uncomfortably or
unpleasantly so. The goal is to “package” the range of input sounds into a
person’s usable residual hearing range, i.e., the area between the impaired
thresholds (e.g. 60 dB) and the point where sound becomes unpleasantly loud
(let’s assume, 95 dB). Ideally, there would also be a volume control that
permits the user to override, at least to a certain extent, the WDRC circuit
(to allow for situational and personal preferences).

· Adaptive Feedback Management. A number of hearing aids on this list
include an effective feedback control circuit, one that uses a technique
that does not modify the frequency response of the hearing aid. When an
acoustic squeal occurs, the hearing aid automatically identifies the
offending frequency and creates an internal cancellation signal. An
effective feedback management system will permit a user to increase the gain
of a hearing aid by 10 or 15 dB without feedback occurring. Open ear fitting
would not be possible without this development.

· Channels and Bands (sometimes these terms are used
interchangeably). The term “channel” usually refers to the ability to modify
compression characteristics, while “band” refers to the ability to change
the degree of amplification of the band (separate from the other bands).
The hearing aids listed in this table display a considerable range of
offerings in terms of the number of channels and bands offered. We should
note that there is little clinical evidence for the presumed benefits of
more than two channels and three or four equalization bands.

· Directional Microphones. Many of the hearing aids listed in this
table include directional microphones. Directional microphones deemphasize
sound signals arriving from the sides and back of a listener relative to
those arriving from the front. Some directional microphones are adaptive,
changing characteristics depending on the location of the noise source(s).
And some are automatic, with the aid itself “deciding ” when to switch
from the omnidirectional to the directional mode. Directional microphones
work best when users are close to the sound source and position themselves
so that the primary signal is in front of them while competing sounds are
at the side or rear (not always possible).

· Noise Management/Reduction Programs. Many of the hearing aids on
this list include an explicit reference to some sort of noise control
program. These have been shown to increase user comfort when listening to
speech, but speech perception ability is not necessarily improved. As far
as I know, when noise (like other people talking) and speech occur
simultaneously, it is not possible to eliminate one without affecting the
other. Still, some people do find a noise management program a desirable
feature in hearing aids, one that makes the listening task less stressful.

· Automatic Telecoil. With this feature, the hearing aid telecoil is
automatically activated when a telephone is placed next to it. It thus
obviates the necessity of the user switching the aid to the “T” position.
Originally, this feature did not permit reception of signals from neck loops
or floor loops, but this has since been corrected (using a different
memory). This feature can be helpful to someone who has difficulty, perhaps
because of arthritic fingers, in switching the hearing aid to the “T”
position.

According to the websites, refinements in the operation of adaptive
directional microphones and noise management systems seem to be the primary
focus of this year’s top of the line hearing aids. For both of these topics,
the promotional materials imply that speech perception (or comfort) in noise
is improved with the new model. However, peer-reviewed studies on human
beings that support these claims seem to be lacking (or is hard to find).
Another creative development includes binaural wireless connectivity, where
two aids “talk” to one another and work in concert. In addition to greater
convenience for the user (since one adjustment controls both aids), this
capacity may eventually lead to improved localization and speech perception
in noise. Another recently introduced development is the inclusion of data
learning (or logging); this feature not only records the listening programs
a person selects, but can also “learn” someone’s volume preference and
adjust the hearing aid setting accordingly. In addition to these
innovations, one can find many other appealing descriptions of new products
by the various hearing aid manufacturers. It makes me wonder what the
hearing aid companies have in store for us next year and whether this year’
s crop will then be relegated to the entry or mid-level categories.

It does seem to be getting a bit overwhelming and I think it may be time to
go back to basics and to focus on what a hearing aid is supposed to do -
help someone hear better. And we’ve known for years what it takes to do
this: a hearing instrument with a large dynamic range that delivers a
wide-band, undistorted speech signal into the residual hearing area of the
hearing aid user (which is located between the thresholds of hearing and
discomfort). It is only after this has been achieved that the convenience
and contribution of special features become relevant. They are important,
true, but mainly in specific situations, for specific purposes (such as
open-ear fittings), and for the convenience of some automatic function. But
hearing better is still what it is all about.

Dr. Mead Killion demonstrated the fact that this can be achieved in a
recent publication (Proceedings of the 2006 International Conference on
Hearing Care for Adults). He reports some interesting conclusions in his
examination of seven different digital hearing aids. In his study, he had
normal-hearing people listen to music through the hearing aids and judge the
fidelity of the recordings. He also measured the ability of two groups of
hearing-impaired listeners to understand speech in noise. As expected, both
speech perception and fidelity scores varied considerably between the
hearing aids. Proving, once again, that all hearing aids are not the same.
What is perhaps his most significant finding was the “nearly perfect
correlation between (a) the fidelity ratings to live music of normal-hearing
subjects and (b) the hearing aid’s ability to deliver high intelligibility
in noise for hearing-impaired subjects.” According to Dr. Killion, in other
words, hearing aids that are judged to provide a “high fidelity” signal for
someone with normal hearing would also deliver the highest speech perception
scores in noise for someone with a hearing loss. And this does not
necessarily have to be this year’s “premium” hearing aid.

So, is the current generation of premium hearing aids worth the cost? It’s
impossible for me to say, since so much depends upon the individual’s
history, communication needs, etc. We should also keep in mind the
following: the more that people pay for a hearing aid, the greater their
expectations regarding its performance. Or, as Dr. Sergei Kochkin found in a
survey he conducted several years ago, the more someone spends for a hearing
aid, the less likely it is that he or she will be satisfied with the value
received. That is, even though a premium hearing aid may be helping someone,
in the person’s opinion, the help received may not be sufficient to justify
the additional cost.

What would I recommend? Unless, some current premium hearing aid includes
some feature that demonstrably benefits a particular person - a possibility
that should not be ignored - I’d suggest that a prospective user first
consider hearing aids labeled as “entry level, basic, or mid-level.” As
noted above, these are not primitive, outmoded devices, but sophisticated
electronic instruments (and once “premium” aids in their own right!). In
terms of hearing improvement, in my opinion most hearing aid users will do
as well with one of these as they would with a top of the line model. Plus
save a bundle of money.

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