The Role of PSAPs in the Clinic



A Conversation between Chase Smith and Brian Taylor

Author: By Chase Smith and Brian Taylor, Au.D.

In April, Mr. Chase Smith and Dr. Brian Taylor conducted a webinar at Audiology Online. The title of the webinar was An Introduction to PSAPs and Hearables. The main focus of their one-hour course was to review the data Chase collected on several popular Personal Sound Amplification Products (PSAPs), and how these devices could be dispensed clinically in the future. Readers are encouraged to find the course on the Audiology Online website. The following conversation between Chase, a 4th year Au.D. student at Northwestern University, and Brian took place a few weeks after the webinar. It captures some of the main points of their course, along with the possible clinical implications of dispensing PSAPs and other hearables.

Taylor: Times sure have changed since I graduated with a Master’s degree in Audiology in the early 90s. One of the biggest changes, maybe the largest since the advent of digital signal processing, is the rise of devices that look like hearing aids, but are labeled as PSAPs.

Smith: I know what you mean. I’ve been surprised by the changes I’ve seen just since beginning graduate school! This is really setting up to be a game changer for our profession in many ways. Not only will large consumer electronics companies be entering the hearing healthcare arena, but new hearing technologies will have much greater feature-sets including health-tracking and onboard data storage options. The products we are seeing now are “the tip of the iceberg” so to speak, this is only the beginning of what is to come.

Taylor: Right. We are only going to see more of them. From what I’ve read, this is a trend affecting all of healthcare. This convergence that you mention has the potential to bring down the silo that surrounds our own profession and the hearing industry.

Smith: There is definitely a morphing of hearing aid technology with common consumer electronic devices. The wearable product category is exploding and, of course, we are seeing the emergence of a new subcategory called hearables, but I am not sure what you mean by silo?

Taylor: I can think of a couple of difference silos. One is the cozy relationship between many audiologists and their favorite hearing instrument manufacturers. I call it cozy because in my opinion audiologists almost exclusively prescribe devices marketed to them by the major manufacturers. We typically don’t even look for newer disruptive technology to recommend to our patients. Think about the last time a patient with a significant communication problem was prescribed something other than a hearing aid. Even though there are plenty of other alternative and complementary products, patients usually end up with a recommendation of hearing aids from one of three technology tiers, or they do nothing. Clinicians tend to live in a very binary world – either the patient is a hearing aid candidate or they are not.

Smith: That seems a little harsh. After all, a lot of clinics offer assistive devices.

Taylor: Yes, and many of these devices have a tendency to collect dust. Do they collect dust because they are ineffective or because audiologist can’t make much money dispensing them?

Smith: It’s probably a little of both, but we have clearly moved beyond the era of the PocketTalker. You did say there was more than one silo.

Taylor: The FDA regulations on medical devices are another silo. Since the beginning of the digital signal processing era in the late 1990’s, the hearing aid industry has been dominated by a handful of manufacturers, and they have slowly dwindled to six global firms today. Of course, these manufacturers have had to follow FDA regulations when bringing their devices to market. In a sense, these regulations are a silo or a barrier to competition. It’s burdensome for new companies to enter a market – even one like the hearing aid industry that’s lightly regulated by the FDA. In the case of hearing aid regulations, it’s not necessarily the regulations per se, but start-up companies have to learn how to manage their relationship with professionals. I know selling directly to consumers is much different that selling a device through a professional, like an audiologist. But for the most part, the FDA has taken a hands-off approach to regulating many of these consumer electronic products, including PSAPs.

Smith: The lack of regulations may ultimately benefit consumers because it provides them with more choices, and more choices may lead to lower prices. But for the clinician, the lack of clear regulations on PSAPs creates a lot of uncertainty. Product quality is highly variable because there is a lack of mandated standards. Because of this, audiologists struggle with recommending and fitting devices that, according to FDA guidance, are intended for people with normal hearing.

Taylor: Good point! As many readers know, in 2013 the Food and Drug Administration (FDA) issued what’s called draft guidance on personal sound amplification products (PSAPs) which said that PSAPs are intended to be used by people with normal hearing in order to enhance specific listening situations like bird watching or hunting. Thus, according to the FDA, PSAPs should not be marketed or sold to people with hearing loss.

Smith: That’s accurate, but I think it’s fair to say many of these PSAPs are being used as amplification devices by individuals with hearing loss. My question is, if these devices can appropriately fit certain hearing losses, why is marketing them to hearing impaired consumers a bad thing?

Taylor: Yes, which is a big reason why the FDA is revisiting this issue. They recently held a meeting with many key stakeholders and they took public comments on regulation of PSAPs as well as other over-the-counter hearing devices. Beyond the politics of regulating PSAPs, I know your Northwestern University capstone project involved the evaluation of PSAPs.

Smith: That’s right, it did! Almost weekly we had patients bringing in advertisements from the back pages of various magazines and newspapers touting a device that looks like a hearing aid, but the phrase “hearing aid” is notably absent from the print. When asked about these, I noticed most audiologists were dismissive of them, but without any solid evidence to back up that attitude. So I sought to learn as much as I could about them so that I could empower audiologists with the tools they need to evaluate these devices themselves--and from that my capstone was born. I gathered together all of the PSAPs I could get my hands on, including ones discussed with patients, and ran them through ten rounds of electroacoustic analysis and real ear measures to see how they compared to traditional hearing aids.

Taylor: One of the lessons from your work is that an audiologist with a hearing aid test box and probe microphone equipment can conduct these measures on any PSAP. I would go a step further and say audiologists could effectively vet PSAPs by applying the criteria for a good sounding hearing aid to PSAPS: A smooth, broadband undistorted frequency response would be a good start for any type of amplification device that will be placed on a human ear.

Most audiologists would agree, and, I think, ANSI hearing aid standards would support that equivalent input noise be less than 30dB. I would argue it should be lower than that, maybe closer to 25dB, if PSAPs are going to be used by individuals with normal hearing or a mild hearing loss. Looking at your data it’s likely many of these PSAPs users will hear circuit noise.

Smith: That’s really what I wanted the take-away of my capstone to be: audiologists have the necessary training, equipment, and know-how to critically evaluate these devices, more so than any other professional. As these devices gain traction in the marketplace, it’s really up to us to take ownership of them and know which ones might be appropriate for certain patients. This knowledge only serves to benefit our patients. Also, I would agree with both of your statements regarding PSAP performance. A common theme among low-cost devices was an inordinate amount of low-frequency gain, making the device inappropriate for those with high-frequency hearing losses. A smooth, flat or gently sloping frequency response is ideal, as it places no inappropriate emphasis on a particular frequency region.

You’re right as well in that equivalent input noise is of great consideration when dealing with near normal or mild hearing losses. According to my research, EIN was around 30 to 35 dB for most devices, and some were even greater than that. This is probably audible to your patient with a near normal or mild hearing loss. This doesn’t necessarily make the device an inappropriate fit, but may affect your patient’s perceived sound quality.

Taylor: Another thing I noticed about your test box measures was the big differences in the performance of the directional microphones, especially between the two conventional hearing aids. I am guessing those differences had something to do with the automatic nature of the microphone’s null steering feature. In other words, the substantially better performance of the Phonak device relative to the GN ReSound device was a by-product of your test parameters and not a design limitation of the hearing aid.

Smith: Directional microphones hold a special place in my heart. There is a large body of research demonstrating significant improvement in understanding speech in noise for patients fit with directional microphone technology. All hearing aids from the six global manufacturers feature directional microphones, and I personally think no patient should be without them. In the low-end devices I tested, none had directional microphones, and even some of the high-end PSAPs that advertised directional microphones showed no directional benefit in my study. As for the difference in performance between the two high-end hearing aids in my study, each device was placed identically in the test box, exposed to the same stimuli, ten rounds were averaged, and each hearing aid was in a fixed directional program. So at this point I can only attribute the difference to differences in processing between manufacturers.

Taylor: Also, you could argue that PSAPs are intended to be used primarily in quiet listening situations by individuals who have near-normal SNR loss, so directional microphones may not be needed. Also, as I recall, directional microphones have more internal circuit noise relative to an omni-directional microphone. Therefore, people with normal audiograms or mild hearing loss are more apt to hear internal circuit noise when the PSAP is in the directional mic mode.

And, another point, I know one of the PSAPs you evaluated has a wireless remote microphone. Considering that remote microphones provide optimal signal to noise ratio improvement, I would argue a remote mic is a feature many users would find extremely helpful – even on a PSAP.

Smith: Yes, you could argue that. The FDA draft guidance suggests these devices should only be marketed to normal hearing people for use in places where normal hearing people would have difficulty hearing, and then lists examples like bird watching, lectures, and hunting. These are all fairly quiet activities. Should these devices be used by those with hearing loss, then they should understand an omnidirectional microphone is not going to help them in background noise. Additionally, even when a device markets itself as having directional microphones, there should be verification performed to determine the efficacy of their directionality, as it may not exist. Research by Dr. Mead Killion suggests that in most environments, a user won’t notice a directional benefit of less than 2 dB, and in cases of open fit, might not notice it until there is at least 5 dB of benefit. If you’re fitting these devices on a near-normal or mild loss, you will probably be using an open fit. So keep the 5 dB rule in mind.

Taylor: One last thing about your test box measures that piqued my interest...you did a really useful measure in which you compared the maximum output at 500 Hz to the high frequency average output, which is the mean output at 1000, 1600, and 2500 Hz. This is a relatively fast way to gauge a broadband vs. narrowband frequency response. To me, this is a really important consideration when evaluating any type of amplifier that will be placed on an ear. I also know of a couple of studies, commonly cited by hearing aid manufacturers, one from Hong Kong 1 and another from Europe2 that indicate most of the PSAPs on the market just two years ago had little gain & output in the high frequencies and over-emphasized the bass response. Obviously, this is an inappropriate frequency response for a patient with a mild, sloping loss.

Figure 1. The OSPL 90 HFA – 500 Hz output ratio for several PSAPs


Smith: A lot of people I worked with would run an electroacoustic assessment (EAA), eyeball the frequency response and then call it a day, which is not necessarily a bad way to do it. Looking at the graph in Figure 1, we can usually recognize when the output appears inappropriate. However, I wanted to give a simple quantitative measure of low-frequency versus high-frequency output, as a way to standardize this process and take into consideration the low-frequency output, which has been of concern with the low-end devices as you mentioned with the previous studies. Those studies found that all tested PSAPs had inordinate amounts of low-frequency gain, making them inappropriate for most high-frequency sensorineural hearing losses traditionally associated with presbycusis. The high-end PSAPs in my study for the most part had appropriate frequency responses (Figure 2), and all but one of the low-end devices had an inordinate amount of low-frequency gain (Figure 3) and virtually no usable high-frequency gain, making them inappropriate for any degree of high-frequency loss.

Figure 2. PSAP with broadband frequency response


Figure 3. PSAP with narrow, peaky frequency response with essentially no high frequency gain


Taylor: We haven’t even talked about Part 2 of your capstone, where you conducted probe mic analysis on the KEMAR. If I remember correctly, you entered a range of hearing loss configurations - everything from a very mild loss to a severe, flat loss to several different steeply sloping losses – into a NAL-NL2 fitting target. Some of your findings were surprising.

Smith: I wanted to see which, if any, hearing losses could be fit by PSAPs. I had heard claims that these devices might be appropriate for mild to moderate hearing losses, but at the same time I had heard that they were inappropriate for any degree of hearing loss. How had anyone come up with these claims when the research was virtually non-existent on this topic? So I took the PSAPs and hearing aids, placed them on KEMAR, and ran real-ear measures for NAL-NL2 targets of ten different audiograms, ranging from very mild to profound hearing loss with seven of those being flat or gently sloping losses and three being precipitously sloping. Fitting to prescriptive targets is the gold standard of the profession, with research showing that APHAB scores were highest for those patients fit to targets and verified with real-ear.

Taylor: For me, one of the main takeaways from your work is that there are a couple of PSAPs currently on the market that can appropriately match a prescriptive target for a moderate flat or sloping loss. A few of these PSAPs can be used for more than a very mild hearing loss. When you think of the time saved not having to fine-tune and tweak a PSAP for a patient that may have some situational communication problems, then making some high quality, vetted PSAPS available in your clinic starts to make sense.

Smith: If you're referring to those patients that come in with one or two specific places where communication is breaking down as situational problems, I see your point.

Taylor: I think most clinicians face this dilemma often: During the case history and communication needs assessment portion of the appointment, the patient is finding it difficult to communicate in specific, often challenging situations. It could be restaurants, cell phones or watching TV shows with British accents. Typically, it’s one or two places when hearing is becoming a problem. You conduct a routine audiological assessment and you find that the patient has no more than a mild hearing loss.

The situational difficulties expressed by the patient exceed the degree of hearing loss measured on the audiogram. Although these patients are often borderline candidates for hearing aids, when you look at their audiogram—and the limited number of situations where they report hearing difficulties, it doesn’t justify the cost of a pair of traditional hearing aids. This is where PSAPs have a place in the clinic, I think.

Smith: I would agree with that. PSAPs offer benefit not only to those unable to afford traditional hearing aids, but also those that may be on the fence about needing them or feel they only need them for certain situations. For those mild to moderate sensorineural hearing losses, these represent an opportunity to try a simple amplification option in these specific listening environments. If they do well with the devices, they may embrace amplification sooner than if the device was not available and graduate to traditional hearing aids at a later date. If they do not do well with them, then that opens up the conversation regarding their hearing loss and possibly the need for traditional hearing aids as opposed to a PSAP. Either way, the patient is gaining knowledge about their hearing, exploring their options, and building a relationship with their audiologist.

Taylor: I bet when we tell these patients with normal audiograms or milder hearing losses that technology doesn’t work for their very real problems in specific listening situations, they begin to look around for alternative solutions.

Smith: Instead of going online to seek a solution, these patients could stay in the practice and become a “patient for life” when we offer high quality PSAPs. The key is to get the patient to try it out, and get them hooked on better hearing. I think this is why this is such a contentious issue. Let’s say PSAPs garner mainstream support, how do we market these as a practice? How do we make sure the consumer actually becomes “hooked” and doesn’t just try them out, end up disappointed, and give up on amplification entirely. Ultimately, appropriate implementation is going to be critical to the success of integrating these devices into our profession. We need these to do more than just amplify, they need to educate.

Taylor: You bring up a couple of important considerations. First, when you mention “appropriate implementation” it underscores the importance of following scientifically-defensible fitting approaches. When an audiologist takes the time to measure the acoustic response of any device while it’s in the ear, to verify it is meeting a specific standard, our profession cannot help but play a valuable service. If the device approximates the standard, say a NAL target, the research tells us the fitting has a very good chance of being successful. A proven approach –even for fitting a PSAP – sure beats the willy-nilly approach of not objectively measuring anything.

Second, what you are describing is what I call a gateway product. It’s intended for the person who is not yet a full-fledged hearing aid candidate, but nevertheless struggles in certain situations. Because many of these listening situations are challenging, an audiologist is still needed to navigate the assorted solutions and educate the patient on their options. With the PSAP, I see the role of the audiologist growing.

Smith: Gateway product is definitely a good term for them. These devices are really targeted towards those with a mild to moderate degree of hearing loss who are unwilling or unable to spend thousands of dollars on a pair of traditional hearing aids, and would instead want to see how basic amplification might help them in difficult listening situations. Plus, I think these devices are almost a gateway product for audiologists in that they really push us to value our professional services independently of technology. These devices are a gateway to an unbundled, fee-for-service model.

Taylor: Great point, Chase. As an experienced clinician, I have to say that it’s refreshing to be able to offer my patients a variety of solutions. I feel like it is one step closer to offering comprehensive patient-centered care. We’ve been talking a lot about PSAPs having basic technology. Do you foresee a day when more advanced technology, like feedback cancellation and automatic directional microphones are available in a PSAP?

Smith: My guess is that advanced features like the one you mention will eventually be offered in PSAPs. If you consider digital noise reduction algorithms an advanced feature, then advanced features are already being placed into PSAPs.

Taylor: Do you think having more features in a lower cost product is good for audiology?

Smith: If you want to grow the market, it’s certainly seems to be a step in the right direction. I remember a study published in a recent issue of Audiology Practices indicating the best performing audiology clinics were the ones who offered the most comprehensive services and technologies. Even just knowing about these products and how to properly evaluate them allows you greater flexibility in helping your patients. Audiologists are the hearing experts, after all.

Taylor: Now is the time for audiologists to start critically evaluating PSAPs, hearables and other technology with an eye toward addressing the needs of to all individuals with self-reported hearing difficulties.

Smith: If readers want the details on my study, they can find them at our AO course, An Introduction to PSAPs and Hearables. A quick Google search will take you there.    
Chase Smith can be reached at chasejcs@u.northwestern.edu.