By Joel M. Mynders, BC-HIS
Hearing aid selection is a critical step in the amplification process. With today’s vast number of choices in hearing instrument technology, where do you start? Part 1 and Part 2 of this 3-part series examined the physical, anatomical, and mobility/dexterity parameters of hearing aid selection, how a Needs Assessment Questionnaire can be used to tailor a hearing aid for a patient’s lifestyle, and how prescriptive formulae are used by dispensing professionals.1,2 Despite the many sophisticated approaches when prescribing a hearing aid, the final question a dispensing professional often asks is: How does that sound? Part 3 addresses how the patient’s perception can be used to assist you in the hearing aid selection process.
The history of using perception as a systematic hearing aid selection method can be traced back at least to the development of Lybarger’s first master hearing aid (MHA).3 The objective in the design of the master hearing aid was to enable the fitter to change performance parameters in the quest for improved judgements of speech intelligibility. Using a MHA, the traditional hearing aid specialist would change settings on the MHA then ask the patient to report whether or not things sounded clearer.
By this technique, the patient selected the preferred settings on the MHA. The chief flaw in this procedure is what happens next: The transition from the MHA results to the actual commercial hearing instrument that is to be used by the client. Over the years, individual MHAs differed from laboratory to laboratory. This resulted in situations where the same performance settings on MHAs did not perform similarly when actual hearing aids were placed on the hearing-impaired individual. The Hearing Aid Industry Conference (HAIC), the manufacturer organization which predated today’s Hearing Industries Association (HIA), moved to work jointly in the development of a master hearing aid to facilitate dispenser/clinic referral fittings in 1959.4 However, this problem was never completely resolved. It should be noted that thousands of people were fitted using MHAs, and the actual hearing aids were adjusted by hearing aid specialists to maximize patient benefit during follow-up visits.
At present, there has been some revived interest in re-establishing the benefits of “perception” as a selection technique. For example, Schweitzer et al.5 detailed a computerized “Method of Adjustment” technique which, in conjunction with more traditional audiological measurements, has been employed by a hearing dispensing network in Europe. Likewise, selection and fitting systems that rely on some subjective responses of the listener can be found in a number of software programs offered by manufacturers.
Certainly, fitting by perception has had a prominent role in hearing aid selection. In fact, an argument can be made that perception techniques never left the field and never will leave the field; at the end of any fitting, the inevitable question to the patient is, “How does that sound?”
The Three Primary Perception-Based Selection Techniques
There are three selection techniques that employ perception as the method for fitting hearing aids. Two of them fall under what Studebaker6 referred to as “direct methods,” and one of them falls under his category of “indirect methods.” The choices under the direct subheading are 1) Judgments of intelligibility, and 2) Paired comparisons. The indirect method entails judgment of sound quality (Figure 1).
Figure 1. More than 20 years ago, Dr. Gerald Studebaker6 diagramed the major hearing aid selection methods. The above adapted figure delineates Direct Methods (which rely on direct assessments of speech intelligibility) from Indirect Methods (which rely on results that are linked to good intelligibility, as well as other factors). Studebaker kept “Quality Judgments” in the Indirect Methods section to show that these factors are not necessarily linked to intelligibility.
Direct Methods. Direct methods involve judgments of intelligibility. This means that the patient judges how intelligible (or relatively intelligible) speech is when listening to various amplification systems (eg, actual hearing aids, master hearing aids, etc). With this technique, “intelligibility” means the proportion of words or sounds heard correctly, generally when using a word-list type test.
This is quite different from a judgment of sound quality via paired comparisons. When using paired comparisons, the patient is presented with two differing acoustic patterns deemed suitable for his/her hearing loss. For this selection process to be effective, the test equipment used must reduce the time-lapse between the sound samples/comparisons. Researchers using paired comparison techniques have found that smaller differences in intelligibility can be found in comparative—as opposed to isolated—judgments; the time elapsed between judgments is critical. The task of the patient is simply to discern which one of the two choices sounds more intelligible.
Some computerized fitting systems have the option of paired comparison selection methods now available in their software (for an example, see Kuk, Keenan & Ludvigsen7).
The approaches and methods presented in this three-part series on the selection of hearing instruments represent an attempt to categorize the wide variety of philosophical backgrounds that dispensing professionals bring to the hearing fitting process and the patient’s they serve. Many hearing care professionals, if not most, believe that “philosophy dictates practice.” The relationship between all the methods covered—including selection by personal needs and lifestyle, selection by traditional audiometric measures and prescriptive formulae, and selection by perception and paired comparisons—should be logical, methodical, empathetic, and synergistic, providing patients with optimal amplification while engendering in them a confidence that will allow them to successfully rejoin the communicative realm of their friends and loved ones.
The various proposed methods can be envisioned as an “enabling” list rather than a “limiting” list. There are now, and will be in the future, other methods that will expedite the selection process and facilitate the transformation of our technology and audiological knowledge into true patient benefit and satisfaction. Likewise, it should be remembered that hearing aid selection is only one part of a comprehensive hearing care protocol that includes, at least: hearing evaluation/assessment; auditory rehabilitation planning and counseling; hearing aid selection; verification; hearing aid orientation and follow-up counseling; and validation and assessment of hearing aid benefit.
As discussed in Part 2 of this series that detailed the evolution of selection protocols, it is evident that hearing aid selection and fitting will continue to evolve. Although a “gold standard” for hearing aid selection may ultimately be good for the hearing aid dispensing field, it is simple-minded and simplistic to suggest that we should all use only “one right selection/fitting protocol” in all cases for the multitude of hearing-impaired patients, or worse, mandate strict adherence to one particular protocol. Rather, it is wiser to consider that each of the methods discussed in this series of articles have merit for certain patients in certain situations.
|Joel M. Mynders, BC-HIS, is a hearing instrument specialist and educator. A graduate of William & Mary, he is owner and CEO of A.P. Mynders & Associates., West Chester, Pa.|
1. Myders J. Essentials of hearing aid selection, Part 1: Cosmetics are not just what meets the ear. Hearing Review. 2003;10(11):26-34, 61.
2. Mynders J. Essentials of hearing aid selection, Part 2: It’s in the numbers. Hearing Review. 2003;10(12):16-20, 51.
3. Lybarger SF. US patent application SN543-278;1944.
4. Skafte MD. 50 Years of Hearing Health Care. Hear Instrum. 1990; [suppl] 41(9):34.
5. Schweitzer C, Moritz MS, Vaughan N. Perhaps not by prescription—but by perception. In: Kochkin S, Strom KE, eds, High Performance Hearing Solutions, Vol 3. Hearing Review. 1999;[suppl] 6(1):58-62.
6. Studebaker GA. Hearing aid selection: An overview. In: Studebaker GA, Bess FH, eds. The Vanderbilt Hearing Aid Report. Upper Darby, Pa: Monographs in Contemporary Audiology; 1982:147-155.
7. Kuk F, Keenan D, Ludvigsen C. Changing with the times: Managing low frequency hearing loss. Hearing Review. 2003;10(12):37.
Correspondence can be addressed to HR or Joel Mynders, AP Mynders & Associates, Inc, 129 North Church St, West Chester, PA 19180.