Dr. Ross on Hearing Loss
Revisiting the Perennial Question: What is the "Best" Hearing Aid?
by Mark Ross, Ph.D.
This is a question that I’ve been asked ever since I became an Audiologist. When faced with two or more devices that ostensibly do the same thing, it is reasonable for somebody to wonder if one would do a better job than another. If this comparison is made with other kinds of devices, and we see from the many examples in Consumer Reports that indeed it does, why then shouldn’t this same logic apply to hearing aids? Well, as a matter of fact, in the early days of Audiology, it did. In those days, the common practice (the “Carhart method”) was to compare a person’s performance with three or four pre-selected aids and recommend the one for which the person obtained the highest speech discrimination scores. The one that achieved this status was considered “best” for that particular person.
The procedure had the kind of face validity that appealed to clients and professionals alike and the method was practiced until well into the l980’s. However, we should recall that at this time hearing aids were generally simple amplification devices, certainly compared to what is available nowadays. In such instances, one could possibly compare the performance of hearing aids, since relatively few electroacoustic variables were involved. But even so, even though the procedure seemed to make sense, in the way it was actually practiced the actual results proved to be unreliable and too time-consuming. In its time, the Carhart method generated literally hundreds of research articles, until it finally died a natural death at about the same time digital hearing aids (and some advanced analog ones as well) were being introduced. So the challenge is much more complicated now than it was then.
In considering the question of the “best” hearing aid, we need to focus on the essential point: it is not the name monogrammed on the hearing aid case that is important, but the composition of the amplified sounds delivered into the ears of a hearing aid user. Manufacturers spend a lot of money with their marketing appeals to develop brand recognition and loyalty, and they do this for understandable economic reasons. But we should keep in mind that all hearing aids serve the same purpose and basically do the same thing: they all respond to acoustic signals and they all deliver amplified sounds into the ear canal. It is what the device does between these two stages, and how the person’s unique communication needs are being accommodated that is the essential question, not the brand name of the hearing aid.
The major dimensions of amplification can be adjusted in most, if not all, modern digital hearing aids; every major manufacturer makes hearing aids that can be programmed to meet “prescribed” amplification targets. Right now, several such prescriptions are generally recognized as optimal goals, at least during the initial selection process; all hearing aids permit later modifications of these prescriptions as guided by a user’s listening experiences. By virtue of meeting these basic prescriptions, all of these aids would be functioning in similar manner. Where differences may occur is the skill in which the audiologist responds to a user’s listening experiences in making required modifications and in the selection and performance of the numerous special features now included in the hearing aids of all the leading manufacturers.
Though they may be labeled differently, all the leading manufacturers make available in some fashion all of the major special features that have been developed in recent years (e.g. directional microphones, compression amplification, feedback management, noise reduction circuits, multi-band amplification, multiple memories, etc.). I say “in some fashion” because these features may be implemented and labeled somewhat differently by the various manufacturers. While all may express the same basic intention in describing a specific feature (i.e., to improve speech-to-noise ratio, reduce acoustic squeal, or control background sounds), they often go about it differently and accomplish their goals with different degrees of effectiveness. But, and this is the central point, it is difficult to ascribe consistent and significant superior listening performance to the totality of the features of any one manufacturer’s hearing aids compared to another’s. For example, the evidence may indicate that a particular feature in one brand may be more effective than another’s (e.g. noise reduction or directionality index), but less effective with a different feature (e.g. feedback suppression). Which aid would be the best overall (and here I am referring to improvements in speech perception, the reason people acquire hearing aids in the fist place)? Would the superiority of one feature in a hearing aid offset the somewhat poorer performance of another feature? We don’t know. To complicate matters still more, in considering any specific feature, the reality is that newer ones are being introduced each year, while existing ones may be upgraded or somehow modified.
More and more it seems, the question of the “best” hearing aid (or amplification pattern) is being defined by the inclusion of the various features that are being included in hearing aids. However, from what I can see the advantages generally ascribed to these hearing aids mainly refer to improved “automaticity,” where the aid makes decisions regarding specific settings (volume control, noise settings, etc) and not necessarily in speech perception abilities. But, even given that a particular hearing aid, incorporating certain features, is preferred objectively and subjectively by some individual, this does not mean that the same positive result will obtain for another person. This is an important caveat and one that applies in spite of all the glowing testimonials offered in support of a specific product, no matter how heart-felt and how applicable it may be for a particular person.
About all we can say that people with hearing losses have in common is that they all have hearing losses! I don’t mean this to be a facetious comment, but sometimes we seem to overlook this basic fact. In reality, it is not just a question of someone falling into the generic category of having a “hearing loss,” but the type, nature, and severity of the auditory disorder displayed by the specific person. This will have major implications in determining what kind of hearing aid the individual should use and how well he or she does with it. We’re all somewhat to very familiar with the basic dimensions of a hearing loss, as visualized in an audiogram. From this chart, we can see how much of a hearing loss a person has across the frequency (pitch) range. The pattern displayed by an audiogram can very considerably between people, with probable significant behavioral implications for the larger variations. Generally, for example, a person with a severe high frequency hearing loss will not function in the aided condition as well as someone with a moderate flat hearing loss (equal hearing loss at the different frequencies). In other words, the same hearing aid will not result in equal performance for these two people. This occurs because the upper limit of possible performance is set by the nature of the auditory disorder and not the hearing aids; because people differ in the severity and nature of their hearing loss, so will their hearing aid performance.
The information provided by an audiogram, as crucial as it is, presents us with only the most superficial information we have about the components of an auditory disorder. Two people with exactly the same audiogram may, and often do, demonstrate completely different listening performance in other auditory tasks, such as their loudness discomfort thresholds and speech comprehension in noise. For example, one such person may find the limits of acceptable loudness to be 80 dB, while the other person with a similar audiogram finds that sounds of 100 dB are easily tolerable. These different tolerance limits will affect the how a hearing aid is fit and how successfully a person performs with it. Such individuals may also differ considerably in how well they understand speech in the presence of noise, though there may be little difference in their speech perception scores in quiet. In other words, auditory disorders and their observable consequences encompass more than what is displayed on the audiogram. These would include, among other dimensions, the ability to detect small time differences within and between speech sounds (temporal resolution) as well as their ability to separate out the individual components in a complex sound (frequency resolution).
Differences in these dimensions explain why hearing aid users with the same audiogram and the same hearing aid may perform differently. But the question still remains; given the nature of some specific individual’s auditory disorder, is there a best hearing aid (or amplification pattern) for that particular person? Certainly, we know from experiences garnered by consumers and professionals over the years, people do perform better, or worse, with one amplification system over another. But is the hearing aid a particular person is now wearing, or contemplating purchasing, the absolute best for that person? I don’t know and furthermore I don’t think the question is answerable at this time, for this reason: we have no way now of determining what a person’s potential speech perception capabilities are to which we can compare his or her actual performance. How do we know when we’ve reached the best possible performance? Additionally, given the awesome flexibility now incorporated in modern hearing aids is it possible that the consumer would do even somewhat better if one or more of the hearing aid’s electroacoustic dimensions were varied in some fashion? I’d say the possibility exists, but there is no way at the present time that we can be certain.
It seems to me that rather than focus on the best hearing aid, potential hearing aid purchasers could more fruitfully spend their time and energy looking for a well-trained audiologist, one who is competent, caring, and conscientious. This is the person whose job it is to select the “best” possible amplification system for a hearing aid user, one who can maneuver between the myriad possibilities now offered by modern hearing aids. Such a person will not only keep up with new developments, but also not limit their efforts to the device itself but will also consider and respond to the totality of a person’s communication problems. The hearing aids these people recommend should ensure that their client’s performance falls into the best possible “zone” of performance, one consistent with the person’s hearing loss, the audiologist’s personal experiences and the research evidence.
So now how do we find this paragon? I don’t have a specific answer to that; I wish I did. . The experiences of other hearing aid users are one major source, as are the recommendations from other professionals (Otologists, etc.). A good place to start would be looking at the professional members of HLAA. You can find one by clicking on the “Finding Your Hearing Health Care Professional” box on the opening page of the HLAA website (hearingloss.org). Obviously, I can’t vouch for the technical proficiency of any of the audiologists on the list, but I can say that their membership in HLAA suggests a consumer orientation that would put them on my personal short list. Someone who functions more like a professional and less like someone simply selling a product. One who recognizes that the implications of a hearing loss can be pervasive and profound and that the search for the “best” hearing aid can best be viewed as just one step, albeit a crucial one, in the effective overall management of a hearing loss.