Textbook of Hearing Aid Amplification: Interview with Michael J. Metz, PhD
Douglas L. Beck, AuD, spoke with Dr. Metz about his rewrite of Sandlin’s book, Textbook of Hearing Aid Amplification, and how things have changed in the third edition.
Academy: Hi, Mike. Great to hear your voice! Thanks for your time today.
Metz: Hi, Doug. Thanks, good to speak with you, too.
Academy: Mike, you’ve done an absolutely wonderful thing…editing, updating, writing, and rewriting and publishing the third edition of Bob Sandlin’s Textbook of Hearing Aid Amplification some two years after Bob passed!
Metz: Thanks, Doug…it was a labor of love. And to be fair, it was a lot easier for me to write and re-write than it was for Bob to create the whole concept and publish the first two editions!
Academy: For those who don’t know, I should start by saying that Bob Sandlin was a very well -known, highly respected, and much-loved giant in the profession of audiology and hearing aid dispensing. His books and his conferences were legendary. In fact, one of the first professional conferences I ever attended (in the mid-1980s) was one of Bob’s events in San Diego. It was an amazing experience for us young pups (at the time) and Bob was so friendly and patient with me…despite the thousand questions I asked him...and that started our 30 year friendship. Nonetheless, please tell me how this third edition came about?
Metz: Bob was always interested in professional education. In fact, when the first edition of the book came out in 1988 (26 years ago), Bob was still very active and for the most part and, as I recall, he promoted that first edition through IHS. However, by the time the 2000 edition came out (the second edition) it had morphed quite a bit into a more sophisticated text and it did very well across the world. In 2009, Bob decided we ought to write a new edition. Bob had some serious health issues at that time and he wasn’t up to the task of re-creating the new (third) edition and I was honored when he asked me to help. We had lots of issues and multiple delays with the original publisher, but the co-authors were totally on board, and we eventually switched publishers. It was quite the journey, and finally, here we are in 2014 and the third edition is done.
Academy: You’ve hit a home run with this one. I think the third edition works very well as a course text for amplification for doctoral students, and it’s very useful for dispensers, too. So let’s get a little into the book itself. Let’s start with the chapter on Speech Perception and Hearing Aids. Bill McFarland suggests as sensorineural hearing increases, people don’t actually need sounds to be concomitantly louder…in fact, what they actually need is an improved signal-to-noise ratio (SNR). I think this point is missed by the public in general and unfortunately, many people in hearing health care, seem to have missed it, too. What are your thoughts on the matter?
Metz: You’re exactly right. One of the things I address in the book’s final chapter, and it’s the major complaint of people who wear (and don’t wear) their hearing aids, is… “I don’t wear the hearing aids because they don’t help me in the situation in which I need them the most (restaurants, cocktail parties, wedding receptions, etc.).” Of course all of us hear this every day. Frankly, there is no correlation between a pure tone hearing test demonstrating a mild-to-moderate (and likely severe) sensorineural hearing loss and a person’s ability to understand speech in noise. The signal-to-noise ratio needed by-and-for the individual to understand speech maximally cannot be determined without measuring it directly through a speech in noise test.
Academy: I agree and I would add that as speech in noise is the single most prominent complaint we hear all the time, and it’s clear to me that measuring the SNR at each hearing and hearing aid evaluation is clearly necessary because we have no way to guess at the magnitude of the problem for the individual, or the success of our solution (whether it be aural rehab, an ALD, amplification, cochlear implants, etc.) without measuring it. And so the point Dr. McFarland made, and the issue which is true for the vast majority of people with hearing loss, is that it’s not about loudness, it’s about SNR.
Metz: Right. SNR is huge and the investigation and inclusion of SNR measures is an area in which most of our colleagues and patients would find benefit. In fact, to me, it’s the first place you should look, especially since it can be easily measured. Of course, Doug, as you know, I’m a big fan of the HINT. I know it’s not readily available, but it’s a wonderful speech-in-noise (SIN) test.
Academy: Yes, the HINT was brilliant…but availability is an issue. So I think it might be wise to look at the QuickSin and the WIN. Of course there are other SIN tests available in 2014, and I have to admit, I think it’s easy to design your own, too.
Metz: I agree…measuring speech-in-noise can be very simple and very easy, and if you’re not doing it, you’re missing a very important feature of any hearing loss. It’s the major issue for the patients, and clearly it should be the major issue for the professionals. And to me, the best test for SIN is the HINT, but it’s hard to get a copy and it does take some time to administer, but it’s my favorite SIN text and it holds up in court. If that’s not available, I recommend the words-in -noise (WIN) test by Rich Wilson and Rachel McCardle. They did a stellar job preparing and norming that one.
Academy: Fair enough. Let’s switch topics and address channels and bands of compression. I know many professionals and consumers think more is better, but have you seen any evidence (peer reviewed) indicating more than 4 to 8 channels give you a better result?
Metz: I think it’s fair to say that many authors and researchers have looked at this and they’ve essentially concluded that four bands are likely adequate, and more than that doesn’t consistently appear to positively impact speech perception, and it seems to me you sure as heck don’t need 20!
The question goes back to the fact that audiologists, dispensers, and the industry rarely publish useful comparative papers indicting what actually works and what doesn’t…and I don’t mean marketing documents. I really mean the same thing you speak about weekly…we need science to lead the way, not case studies. Further we need control and experimental groups and randomized controlled trials with substantial numbers of participants, so the data lends itself to accurate and reasonable statistical analysis. That is, we spend so much time worrying about trivial things that have little science behind them, that we sometimes miss the big things. For example, you and Sergei Kochkin and more than a dozen prominent authors published that study in 2010, which showed conclusively that the education level and/or the degree the practitioner held was far less important than their knowledge and adherence to best practice protocols…but it seems that few people use best practice protocols, and I think that’s why many people acquire their hearing aids via the internet and direct mail. That is, most hearing aids are dispensed using poorly defined or ill-advised protocols, and the patients want proven technologies or protocols – or there’s little reason to see the professional, as was obvious in Kochkin’s newest 2014 article.
Academy: Yes, well those are very solid points, Mike. And as you know, the marketplace is changing rapidly, but for those who embrace the changes and understand why they’re happening, and realize the advantages of a high quality product and a best practice protocol, the future is bright! But clearly, you cannot practice in 2014 the way you practiced in 1994. It simply makes no sense and won’t work.
Metz: I agree. And to be clear, change doesn’t have an endpoint. That’s the whole concept of being a lifelong learner. And frankly, the practices and people that don’t change with the times are on a dead end street. It’s really important to remember there are many, real and modern threats which impact our practices and our profession and these outside influences impact and change everything. That’s the way life goes. You cannot stand still. If we don’t maintain and improve our skills and worth, and if we don’t fight for our piece of the pie, it’ll vanish as others are ready and willing to get involved.
Academy: Okay…let me change subjects again. Let’s get back to the book! Please tell me your thoughts about extended bandwidths?
Metz: In general, and quite simply, a wider bandwidth is better. That is, as the bandwidth becomes wider (up to 8,000 or 10,000 Hz), the quality of sound improves, it becomes possible to maintain spatial cues (ITDs and ILDs), speech in noise improves, music is more pleasant, and on and on. There are actually no advantages to narrower bandwidths and I’m very happy to see most or all of the major manufacturers offering extended bandwidths in their standard and power products.
Academy: And if you don’t mind…let me get your thoughts on remote microphones, as I recommend they should be included in virtually every hearing aid fitting for adults.
Metz: Yes, I tend to agree. Remote microphones are a bit tricky because it’s something else to take with you and learn to use. But, for the person in a crowded restaurant, or cocktail party, they’ll certainly enjoy a vastly improved SNR using a remote microphone than they would had they used top-shelf, premium hearings aid in that challenging and difficult noisy environment. However, many adult patients are not capable of using an accessory with their hearing aid(s), and still others would not opt for remotes in spite of the demonstrated advantages. Many patients enter into hearing aid use expecting the circuit technology to solve all their hearing problems. I think that those unfulfilled expectations are quite significant.
Academy: And what about the most significant improvement in digital hearing aids in the last decade or two?
Metz: To me, feedback reduction is at the top of the list of most significant and beneficial. It allows us to provide more gain than ever exactly where it’s needed. Further, feedback reduction technologies have allowed us to employ RITEs and RICs in ear canals that would have been impossible ten years ago.
Academy: Mike, you’ve been very generous with your time. One last issue before I let you run. The book’s final chapter asks “Will technology replace the clinician?” Please tell me you thoughts on this.
Metz: Well, Bob and I had lots of discussions about the future—not only the future of hearing instruments but also of the future of audiology. I want to urge professionals to do the things they’ve been trained to do, to do the right tests for the right reasons and to recommend and fit technology based on science, measurements and data, not case studies or presumptions or any other unproven strategies. We concluded that technology will very likely ultimately replace the clinician. As time moves forward, technology improves and we will have need less need for the professionals. That’s just a fact, and it’s not necessarily a bad thing. You already see this in medicine. People can figure things out via the Internet to which they never had access before. You know, sometimes the professionals are often not much smarter than those they serve. The difference sometimes is access to the information, and now, everyone has more access.
Academy: Okay, Mike. It is a total joy to speak with you and I love the book. Thanks for your dedication to task and for carrying Bob’s legacy forward!
Metz: My pleasure, Doug. Thank you for your interest and I hope to see you soon!
Michael J. Metz, PhD, is an audiologist, author, and editor of Sandlin’s Textbook of Hearing Aid Amplification.
Douglas L. Beck, AuD, Board Certified in Audiology, is the Web content editor for the American Academy of Audiology.