Clinical Topics in Hearing Aid Research: Interview with Jason Galster, PhD
Douglas L. Beck, AuD, spoke with Dr. Galster about his new book, Clinical Topics in Hearing Aid Research, as well as spatial cues, localization, microphone placement, tinnitus inventories, speech in noise, and more.
Academy: Good morning, Jason. Great to speak with you.
Galster: Hi, Doug. Thanks for your interest in the new book!
Academy: Entirely my pleasure. Let me start by noting your new book, Clinical Topics in Hearing Aid Research, was a collaboration between you and your co-author, Katherine E. Stevens, PhD.
Galster: Exactly. Katherine is my colleague and her practice is in Buffalo Grove, Illinois, and is named Long Grove Audiology.
Academy: Very good. And while we’re on affiliations….I know you’ve been with Starkey Research for a few years now, and you manage a clinical research group. So then…let’s talk about the book. I think you and Katherine have initiated a wonderful and rather new concept in book writing. First of all, you’ve self-published the new book, which helps keep the cost down, and the other thing that’s very cool, is the book appears to be a translational delight. That is, the two of you took research papers from the peer-reviewed journals, and then you discuss them with an eye toward clinical application. Is that a fair analysis?
Galster: Yes. That’s exactly the concept. We took research papers that are very topical and we divided them into sections addressing the physical characteristics of hearing aids, the features of modern hearing aids, patients with hearing loss, and prescribing hearing aids, and we revealed the key concepts and applicability to everyday hearing aid fittings.
Academy: That’s a wonderful idea and I suspect there’s a very real need for this book as precious few audiologists have the time to read and think through the most current research articles. How long did it take from concept to paperback?
Galster: It was about three years in the making. So it’s certainly been a challenge, but also a labor of love for the two of us. One example comes from the literature on tinnitus. Many clinicians are familiar with the Tinnitus Handicap Inventory (THI). The THI is clearly well known, well researched, and in fact, I know you’re an advocate of the THI, Doug. But for this book we got to examine other tinnitus assessment tools. And, after a thorough analysis, I have to say the Tinnitus Functional Index (TFI), which is very new, clearly has some advantages and assets that we address in the book.
Academy: Very good. Thanks Jason. I’ll have to review that. In the meantime, I recall you addressed some interesting notes and thoughts on microphone location, spatial hearing and neuroplasticity?
Galster: Right. Spatial hearing involves the ability to separate or isolate streams of acoustic information arriving from multiple, simultaneous directions. Further, the brain is very plastic (i.e., malleable) in young people, and remains plastic throughout the lifespan. Of course, it certainly seems that very young children have the most plasticity, and as you know, plasticity does decrease as age increases. In the book, we address the fact that if a patient is wearing a behind the ear (BTE), and you switch them to a completely in the canal (CIC) (with a very different microphone location), initially, their brain doesn’t (generally) accept that change very well as the acoustic signal has changed quite a bit. However, over some 30 days, you will see improved localization ability as the brain re-learns the new microphone location and how to use the new acoustic cues offered by the pinna.
Academy: So then, is there a particular style of hearing aid that maximizes spatial cues, or will the brain learn to adapt to whichever style is provided?
Galster: That’s a fantastic question. In some cases, it’s advantageous to use an open fitting; for instance, people with good hearing in the mid and low frequencies may appreciate the open-canal and unimpeded use of their residual hearing. However, as the hearing loss in the high frequencies increases, it’s a good idea to consider canal placement of the microphone to provide improved spatial information. Of course we would need to specifically define the exact microphone location and the exact hearing loss in the high frequencies, but in general, microphone placement is an important factor in capturing and maintaining spatial cues, and placing the mic deep in the canal is very useful for maintaining high frequency acoustically-based spatial cues. And to be clear, when using a BTE hearing aid, you’ll simply not have access to the spectral information the pinna generates…and so, yes, placing the microphone as deeply as you can in the canal is a good thing with respect to preserving spatial cues and maintaining or improving localization ability.
Academy: I totally agree. Let’s address another specific issue from the book. What about temporal resolution….what’s that all about?
Galster: You’ve identified one of the really important and arguably lesser well known issues in hearing loss and hearing aids. People with sensorineural hearing loss have all sorts of perceptual distortions as a direct result of their sensorineural hearing loss. For example, they have loudness, spectral and timing distortions, some of which are exacerbated by hearing aid use. And perhaps the key point is that people with the worst temporal resolution do the worst with regard to speech in noise, and of course, not understanding speech in a noisy background is the most common complaint each of us addresses.
Academy: Absolutely. In fact in my presentations, I often state that speech in noise difficulty is the number one reason people come to see the audiologist, it’s the number one complaint of hearing aid users, and it’s the number one problem for people (children in particular) with auditory processing disorders!
Galster: Exactly. And so it’s important for hearing aid developers to consider timing issues in their signal processing. The right combination of strategies can maximally maintain the natural acoustic cues. This is a challenge all manufacturers need to address. In fact, most hearing aids available today, perhaps 2/3rds or so, have asymmetric processing delays across frequency; what this means is that the hearing aid presents low frequencies several milliseconds before high frequencies – which only introduces further distortion to spectral perception, resolution, and other psychoacoustic aspects.
Academy: Absolutely. And for patients with or without hearing aids, there was a new, 2013 article from Northwestern University that demonstrated that temporal cues are able to be improved through commercially available software…and that was a huge finding!
Galster: Yes, I saw that, too. I think this has the potential to be a game changer and I hope the profession and hearing aid developers are able to get their arms around these concepts!
Academy: Okay, switching gears here…you guys have a nice discussion about over the counter (OTC) hearing aids, such as PSAPs, mail order, and hearing aids purchased through the Internet. Can you tell me a little about what you’ve learned?
Galster: Absolutely. The research does show there are higher and lower quality products available OTC. However, the issue is that without appropriate fitting protocols, I believe you remove the essence or the hub of quality care. So the OTC patient doesn’t get a diagnosis and perhaps more importantly, he or she never learns his or her medical, surgical or audiological options…which of course, can put the patient in a very dangerous and sometimes life-threatening situation. Beyond that, without appropriate counseling and aural rehabilitation, it’s just as likely that an excellent OTC hearing aid will fail as succeed.
Academy: Yes. I use the analogy that you can buy a fantastic Porsche or Mercedes Benz and then you’ll own a phenomenal car—but if you don’t have a license and you don’t know how to drive, the car is not going to be of much use!
Galster: Exactly. And I might take it quite a bit further and mention that without real-ear and without outcomes measures (i.e., verification and validation measures) there’s a very good chance the patient doesn’t understand where they are most challenged and where their opportunities for success exist. Illustrating these things to any patient certainly helps to ensure their success.
Academy: Thanks, Jason. I appreciate your time and energy and your thoughts on these matters. I think the book is unique in the audiology literature in 2013/2014, and I think it boils difficult concepts down to their basic, core essence. I strongly recommend this as a “getting up to speed” book for practicing audiologists.
Galster: Thanks, Doug. I appreciate your time, too.
Jason Galster, PhD, is the co-author of Clinical Topics in Hearing Aid Research.
Douglas L. Beck, AuD, Board Certified in Audiology, is the Web content editor for the American Academy of Audiology.