Editor’s Note: For our regular readers, you will notice that our Hearing Health section has now become Hearing & Hearing Aid Technology. We have decided to expand this section to focus on technology and the latest innovations in the hearing industry. It is our hope that you visit here often to keep up to date with the latest developments.

Today, we bring you a discussion by our Hearing News Watch editor, Brian Taylor, AuD, on using clinical judgement to determine when hearing aid circuit noise is a problem. Today’s post is part of Brian’s “Signal & Noise” series, which is a bimonthly column at Hearing Economics.

 

Hearing Aid Circuit Noise: Using Clinical Judgment to Know When it’s Really a Problem

 

Brian Taylor, AuD

Brian Taylor, AuD

Recall the last installment of Signal & Noise discussed the clinical implications of a recent study from research audiologists at Vanderbilt University Medical Center. If the numbers in their study held true across the entire profession, clinicians would send back virtually every hearing aid because they fail to meet the ANSI specification for equivalent input noise (EIN).

For the industrious clinician, who systematically evaluates every device in a hearing test box with the appropriate coupler, sending a lot of hearing aids back to the manufacturer and rescheduling patient appointments is ruinous to the business for obvious reasons. Good judgment and some attention to research can help address this problem and keeping patient’s happy & clinic flow efficient.

 

Standards vs. Specifications

 

At the heart of this issue is the difference between an industry specification (what we call an ANSI “standard”) and a hearing aid performance standard. Let’s take a more careful look at this difference, and how it relates to the practice “good audiology.”

A performance standard is typically developed according to a specific set of rules and procedures with broad agreement among many interested groups. For example, hearing aid manufacturers, clinicians, and other stakeholders could convene a group and create a hearing aid performance standard.  Once a performance standard is created, it is published by a neutral party for everyone to follow. To the best of my knowledge this has not been done for hearing aids, however, any of the scientifically-derived prescriptive fitting formulae, like the NAL or DSL family of targets, are, in a sense, a performance standard.

On the other hand industry specifications – like the ANSI hearing aid “standards” (I would argue they are specifications and different than a standard per the definition above) – have a different purpose.  Industry specifications are used as a reference for design or product criteria. They provide a common set of definitions and tests that allows agreement throughout the industry. Further, the ANSI hearing aid “standards” provide a level playing field with which to test hearing instruments produced by all manufacturers.

 

When clinicians take the hearing aid out of the package, place it into the hearing aid test box in test mode and compare it to the printed specifications that accompany the device, they are answering the basic question: Is this hearing aid performing within a group of defined specifications?

 

The Peculiarities of Measuring Circuit Noise in the Clinic

 

Audiologists must be involved with following both specifications and standards, because at the end of the day, no matter how sophisticated or expensive the hearing aid, there are three things we need to get right:

 

  1. Do no harm. Ensure the amplified incoming sound is not unintentionally or undesirably altered by the hearing aid.
  2. Restore audibility. Ensure the amplified sound is above the patient’s threshold,
  3. Control the output. Ensure the amplified signal does not exceed the patient’s loudness discomfort level

 

It is point #1 – do no harm – that warrants our attention to circuit noise. The Holder et al study tells us that many modern hearing aids fail to meet the ANSI equivalent input noise (EIN) specification. But, a high failure rate on the EIN specification may not reflect a problem with the hearing aid fitting. According to the engineers I contacted, high EIN numbers might be artifact resulting from measuring a nonlinear hearing aid with its expansion feature activated. Recall that the EIN specification requires that the high frequency average gain for a 50 dB input be subtracted from the output when no signal is being delivered. This assumes the gain of the hearing aid for a relatively soft 50dB input is a valid reflection of gain needed for everyday listening. Thus, the EIN measure may not be a valid measure of circuit noise in typical listening situations.

The dilemma for the clinician is determining when circuit noise exceeding the EIN specification by more than 3 dB is really a problem that requires the hearing aid to be sent back to the manufacturer or more of a situation that does no harm to the patient. To address this dilemma let’s turn to some research.

A 2010 JASA study published by James Lewis and colleagues at the University of Iowa, investigated circuit noise in modern hearing aids. They evaluated the circuit noise (EIN) of hearing aids from six manufacturers and found that circuit noise is generated from components other than the microphone, and this circuit noise is often dependent on the input level of the incoming signal.  They also found that certain adaptive features could make circuit noise worse. Maybe some of those adaptive features that provide additional benefit have the opposite effect of causing harm (annoying & bothersome circuit noise)?

 

Avoiding Harm

 

One important consideration from the Lewis et al research and perhaps the one point that is most clinically relevant is the EIN measure by itself is really not all that important. It’s the relationship between the EIN measure and the patient’s threshold that really matters. For example, if you have a patient with relatively poor thresholds, say worse than 40dBHL, even high amounts of circuit noise won’t be audible. On the other hand, even if a hearing aid had low EIN, if the patient has normal or mild loss thresholds, it is possible that even relatively low levels of circuit noise could be audible.

 

It takes sound clinical judgment by the audiologist to know when an EIN measurement outside the specification might be a problem for the patient.  

 

Here is another important consideration that requires good judgment: Just because circuit noise is audible doesn’t mean it’s annoying or bothersome to the patient. As Agnew (1997) demonstrated on a group of eight subjects with moderate loss, hearing aid circuit noise became audible at frequencies between 500 and 1500 dB when the noise reached intensities of 20 to 35dB.  The difference, however, between audible and bothersome circuit noise ranged from 4 to 15dB. Since even small increases in audible circuit noise can make it bothersome for some individuals, audiologists need to carefully monitor its presence.  

Based on these two papers and a couple of conversations and e-mails exchanges with industry engineers, here are a few things you can do in the clinic to ensure that potentially high levels of circuit noise are not doing patient harm.

 

  • Using your hearing aid test box, measure EIN, but as Jim Jonkman, an engineer at Audiscan shared with me via email, “The challenge in the clinic has always been to make a solid EIN measurement and that’s due to ambient sound contaminating the measurement. Even if only one impulsive sound gets into the EIN averaging window, it can easily dominate the average and give a higher EIN than that produced by the device alone. The ambient sound can come from many sources, but a significant one often overlooked is vibrational pickup into the test chamber. Vibration picked up from a laptop on the same table, a mouse being moved on the desk, or even a door closed in an adjacent office can all become sources of unwanted sound potentially coupled into the test chamber. Any sort of impulsive sound occurring during the EIN measurement will easily skew the average and that will show up as a variation in the repeatability. To confirm that the setup is suitable for an EIN test, it should be run in the calibration condition with no device attached. It should be able to achieve a repeatability of 1 dB at the rated value for the equipment.”

 

  • During the fitting appointment, listen for audible circuit noise. This is a good practice for all fittings, but especially for patients with normal low to mid frequency hearing or a mild to moderate loss through 1500 Hz. It can be done if your fitting room is in a sound-isolated space and you have a pair of high quality earphones that can be plugged into your probe mic system. With the hearing aids turned on and without an input signal, while wearing your earphones in your quiet room, listen for circuit noise. Ask your patient if they can hear it. If they can hear it, don’t panic, audible circuit noise in quiet doesn’t necessarily translate to being bothersome. This observation is something that needs to be monitored over time.  (Back in the pre-digital era, when circuit noise came almost exclusively from the microphone, with the hearing aid turned on in the patient’s ear, you could plug the mic port with putty and if the noise remained the circuit noise was a likely culprit for poor sound quality. Given that circuit noise in a non-linear device with other automatic processing schemes may be generated from components other than the microphone, this technique of plugging the mic port and listening for circuit noise may no longer be quite so effective)

 

  • After you’ve conducted this routine measurement on several hearing aids from different manufacturers, you might be able to identify makes or models of hearing aids that have consistently low circuit noise. Stick with these products for patients with normal hearing and mild hearing loss through 1500 Hz.

 

Identifying annoying & bothersome circuit noise from audible circuit noise which may be outside the ANSI specification requires a skillful audiologist. Although technology is rapidly becoming more automated, the good judgement of an audiologist to first do no harm is something that never goes out of style.

 

 

Brian Taylor, AuD, is Senior Director, Clinical Affairs, for Turtle Beach/Hypersound.   He continues to serve as Editor of Audiology Practices, the quarterly publication of the Academy of Doctors of Audiology. During the first fifteen years of his career, he practiced clinical audiology in both medical and retail settings. Since 2005, Dr. Taylor has held a variety of leadership & management positions within the hearing aid industry in both the United States and Europe. He has published over 50 articles and book chapters on topics related to hearing aids, diagnostic audiology and business management. Brian has authored three text books:  Fitting and Dispensing Hearing Aids(co-authored with Gus Mueller), Consultative Selling Skills for Audiologists, and Quality in Audiology: Design & Implementation of the Patient Experience.  His latest book, Marketing in an Audiology Practice, was published in March, 2015.  Brian lives in Golden Valley, MN with his wife and three sons.  He can be reached at brian.taylor.aud@gmail.com or brian.taylor@turtlebeach.com.

 

*feature image courtesy of Cambridge in Color

 

By Dennis Kraus, Audio Infos Germany

 

At the IFA preview in early July 2016 in Hamburg, ReSound Germany Executive Director Joachim Gast explained to Audio Infos Germany why the company decided to have its own stand at big consumer electronic fairs like the IFA in Berlin or the Mobile World Congress (MWC) in Barcelona, and what benefits a manufacturer of hearing systems can expect from this kind of event.

 

At the IFA Preview in Hamburg, Joachim Gast explains the benefits of smart hearing systems to moderator Peter Becker.

 

Mr Gast, ReSound is not only an exhibitor at the Berlin Consumer Electronics Fair but has also decided to attend the three IFA preview events in Berlin and Hamburg. What motivated you to attend the previews as well?

 

We have been represented with a stand at the IFA since 2014. And we will be there again this year to inform journalists about the topic of connected hearing aids and fitting in specialist stores. These preview events are good opportunities for us to demonstrate, in a smaller context, what we can do technically. Because here we reach the journalists at a time when they are gathering information about trends for the upcoming IFA. We manage to do this very well at the preview events. We also get a chance to make appointments for the IFA stand in Berlin.

 

So you are interested in making contact with journalists from outside the hearing sector – and is that why ReSound also attends events beyond industry-specific ones?

 

Exactly. We’re trying to get the best of both worlds. We are a developer and manufacturer of medical devices and that’s what we plan to remain. But we can only grow if the sales of our clients also grow. As a result, we try to make a contribution by initiating contacts with journalists from outside our sector to increase awareness about the topic of hearing loss that is so important for individual people but also for society in general. We can also present smart, connected ReSound products that are fitted by hearing aid specialists.

And we can best do this if we talk to journalists who are reporting on the omnipresent topic of “connectivity” and who are also interested in cross-sectoral connectivity. This covers everything in the area of the smart home, home appliances with voice output for example, because this is only really useful if the voice output is streamed to ReSound devices in the future. For audio-based apps, we have already had connectivity between iOS products and ReSound since 2014. And journalists who write about this can best be reached at the IFA.

 

What has your experience been of the IFA until now? After all, here you are not among other providers from the hearing sector, like at the EUHA congress, but with Samsung, Garmin, BenQ, SanDisk, etc…

 

When we signed up for the IFA in 2014, there wasn’t even a category for us as a manufacturer. At that time, we were simply classified under “11.3 Other”. But now, there is an IFA category for “smart hearing aids”.

 

So the fact that this category exists is largely due to ReSound…

 

We could say that ReSound initiated this IFA category. At any rate, our presence over these last three years has increased awareness among the IFA organizers that this is an important product area that also has high social relevance. We have come from a point where no one really knew where to fit us in to today, where we have become established as the reference for smart, connected hearing systems.

 

Once you have sparked a journalist’s interest, what topics come up and what do they want to know from you?

 

There are many questions. We always start with the fact that our products are not from the consumer electronics area and are therefore not available at electronics stores, but rather in specialist hearing aid stores. When we mention that there are more than 6,000 of these specialist stores in Germany, people are usually very surprised. We then explain about hearing loss and how individual it is. We then move on to the topic of the smart, connected solutions that are already available: sound streaming from an iPhone, control through our ReSound smart app on Samsung Galaxy, and various Apple products, including the Apple Watch. Most people we speak to find this really interesting because the journalists do not expect this type of thing from a hearing aid.

 

Do the design awards that ReSound has already won help you? I see you have set them up here today too?

 

They help us in that they somewhat enhance media attention. But they are not our main concern. When we attend events, we also like to take part in the award proposals. And the jury’s reasoning when we are awarded a prize shows that we communicated the message very well. For example, the fact that additional functionalities such as audio streaming or the app – docked onto a conventional medical device – reach people and bring them tangible added value for their day-to-day lives.

But like I said, an award application is not a focus point for us but rather a side line that is useful for us to get in contact with journalists.

 

Since you are interested in making contact with journalists, are there other important events for you, in addition to the IFA?

 

The German Team at ReSound is of course not alone in this area. For instance, our international ReSound colleagues were present at the Mobile World Congress in Barcelona. I had the pleasure of attending personally to share our experience of the IFA. So there are similar events internationally. Another example is the CES in the United States, that is held each year in Las Vegas, Nevada and which our US colleagues at ReSound like to attend. But I must say that we also watch how we spend our budget, so for us in Germany, the focus is clearly on the EUHA Congress and the IFA.

 

Do you also make the most of the IFA to network with other companies that offer technologies that may be of interest to ReSound?

 

Absolutely. That is one of our goals. We get to talk to firms that are not in our sector to make them more aware of the topic of connectivity and to show them the added value of audio-connectivity in day-to-day life. In this area, we also get a lot of interest from representatives of other sectors who, of course, do not know our sector, or not well in any case. But when we show what is already possible technically at ReSound, and the added value the solutions bring to the user, people are very impressed and highly interested. So we attend the IFA to make contact with journalists and other people from companies that we can partner with.

 

But as an exhibitor at the IFA, you must get quite a lot of interest from potential end users.

 

The admission fee is low at maximum 17 Euros, which means that many private individuals visit the IFA. Of course, we also provide information to private individuals who come to our stand, as well as potential hearing aid wearers or their relatives. If people are interested in hearing aid fitting, we adopt a very pragmatic approach and refer to the “Find a professional” section of the ReSound homepage, to find the nearest hearing aid specialist who has listed our products.

 

Mr Gast, thanks very much for your time!

 

 

awnEditor’s Note: By mutual agreement,  this article is republished with permission from Audiology World News, where it originally appeared on November 29, 2016.