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Dr. Ross on Hearing Loss

Premium Digital Hearing Aids

by Mark Ross, Ph.D.
This article first appeared in the
Hearing Loss Magazine (Mar/Apr 2008)

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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