by Brian Taylor
“Signal & Noise” is a bimonthly column by Brian Taylor, AuD.
Recent FDA regulatory chatter concerning hearing aids, combined with the rising availability of automated technology is making audiologists nervous – – and rightly so. It certainly seems plausible we are embarking on an era when the skills and expertise of the professional are no longer needed – that the current approach to delivering services to patients is becoming obsolete.
The purpose of this 2017 series of Signal and Noise articles is to demonstrate even in the face of disruptive changes that “good audiology,” which is some undefined combination of science and art, is more important than ever. It does, however, require re-engagement with some basic scientific principles and re-imagining how we can create value for today’s savvier consumer.
Part 1: Quality Control & Hearing Aid Failure Rates
Let me go out on a limb and suggest that many audiologists believe in a myth: that incrementally improving digital hearing aid technology has somehow negated the importance of quality control in the clinic. It seems many of us really believe that we have somehow arrived at a time where the hearing aid technology is so good that we can make assumptions about quality control. Simply stated, too few hearing instruments specialists and audiologists take the time to cross check their hearing aids to ensure they are meeting the current ANSI standards. And. in light of a recent study addressed below, it is troubling to think how many patients were fitted with devices performing outside of an established standard.
The quality control of hearing aids, as most know, has been regulated since 1976 when the FDA adapted the American National Standards Institute (ANSI) S3.22-1976 Standard Specification of Hearing Aid Characteristics. Since then, manufacturers are required to adhere to these standards or risk a steep penalty. Over the past 40 years there have been several updates to the standard, the most recent being in 2014.
Even though hearing aid manufacturers must demonstrate they closely follow these quality control standards, professionals, who directly interface with consumers – whom these types of quality control guidelines are intended to protect – are not mandated to ensure these standards are met prior to dispensing hearing aids. Table 1 is a summary of the most current ANSI hearing aid standards and their accompanying tolerances.
Full on gain
Full on gain
Full on gain
Reference test settings
Reference test settings
Attack & release times
Reference test settings/Max AGC
+/-5 msec or +/-50%
Systematic and Unsystematic Failures of Quality Control
A timely study by Jourdan Holder and her colleagues at Vanderbilt University Medical Center, published in the September 2016 issue of JAAA, addressed both the discrepancies across hearing aids relative to the ANSI standards and the potential limitations of these current standards.
Using standard equipment found in any ordinary dispensing practice, Holder et al tested 73 hearing aids, representing four brands, to determine the number of devices in compliance with the ANSI standard. Although not part of the ANSI standard, they also looked at the quality of directional microphone processing.
In order to properly complete the ANSI testing, the researchers attempted to obtain the recommended testing protocol from the manufacturer. In the article they report that getting the specific protocol from the manufacturer was arduous, and often required communicating with many different individuals at the company. (An observation that demonstrates a lack of standardization in our profession) Once they obtained the specific instructions needed to complete the measurements, the researchers investigated two different types of situations in which hearing aids may fall outside of the ANSI specification range: Unsystematic and systematic discrepancies.
As Dr. Holder recently told me via email,
“Unsystematic discrepancies are the traditional quality control issues with which we are all familiar. These occur when a measurement is out of specification possibly due to damage, breakage, or a component failure. We found in our study these discrepancies occur randomly and relatively infrequently, between 2% to 11% of the hearing aids tested, depending on the brand.”
A random failure rate of around 10% seems awfully high, especially when this equates to about a 1 in 10 chance the product you are about to fit on a patient has a quality problem. The researchers point out, however, that their measured unsystematic failure rate of between 2% to 11% is much lower than previously published reports from the 1980s.
Dr. Holder went on to describe the other type of failure rate they investigated in their study:
“Systematic discrepancies, on the other hand, are the discrepancies, which were a more surprising finding in this research. You can think of systematic discrepancies as a measurement that you might come to expect to be out of compliance in a certain pattern for each manufacturer. In other words, systematic discrepancies suggest that particular brands are prone to specific quality control issues. In the current study, we selected one hearing aid model from four brands. We documented a specific pattern of systematic discrepancies and then confirmed that this pattern persisted with other models within the same brand.”
Some Things Amiss
The researchers found that none of the 73 instruments were within the allowable ANSI tolerances for every specification. All four brands scored 100% compliant on only two specifications: MaxOSPL90 and directional microphone performance (not part of the ANSI standard, but nevertheless a critical component in need of quality control).
On the other hand, all four brands evaluated in the study had varying degrees of problems with HFA-FOG and EIN (equivalent input noise). Specifically, three of the four brands had 10% of more of their hearing aids undershooting the FOG standard by more than 5dB, with just 7% of hearing aids from one of these brands performing within the tolerance for HFA-FOG.
Perhaps more problematic, circuit noise (EIN) outside of the ANSI specifications was found on all 73 hearing aids tested. A 100% failure rate on one measurement of the ANSI standard does not add up. Clearly, something is amiss, and as the authors point out, the source of these systematic discrepancies could be the manufacturing process, the manufacturer’s measuring protocol or systematic errors in how the measures are conducted in the clinic.
The researchers took several steps, outlined in the article, to minimize errors associated with clinical measurement errors. That leaves us the manufacturing process or the manufacturer’s measuring protocol as the possible sources for these systematic discrepancies. That prompted me to reach out to my friend, John Pumford. John is one of the most thorough and detailed audiologists I know, and he has first-hand experience in the hearing aid manufacturing and equipment world. John had this to say:
“While many manufacturers do their best to ensure delivery of quality product, there are cases where the devices we receive do not perform as expected upon receipt as conveyed in research and anecdotally by those dispensing hearing aids. Environmental factors can serve to impact the performance of hearing aids during and after manufacturing, particularly if these aspects are not tightly controlled. Measurement tolerances on specification measures can result in devices being provided that are on the boundary of a passing grade prior to being subjected to the shipping and handling process.
Further, research such as that recently conducted by Holder and colleagues this past year has shown that there can be large systematic differences between reported and actual quality control measurements as conveyed in ANSI tests. While the reasons behind their findings can be debated, I believe it only further supports the ‘best practice’ viewpoint that it is in the best interest of both the clinician and the patient to ensure dispensed hearing aids are functioning properly and as advertised – and the only way to know for sure is to actually measure their performance. Quality control assessment upon initial receipt of product can allow the clinician to avoid unnecessary follow-up visits to address problematic instruments and/or prevent the need for rescheduling due to a faulty device – not to mention increase the likelihood that the hearing aids will function optimally for the listening needs of the patient. What may appear to some to be a misuse of time up front in a busy dispensing practice can actually serve to save time, lessen frustration and improve patient care in the end.”
Take Home Tip
Based on the Holder et al study and the advice from Dr. Pumford, clinicians need to measure the performance of every hearing aid against the ANSI standard prior to dispensing it. To complete this task, use the fitting software to place the hearing aids in the Test Mode (adaptive features are deactivated) If you can’t find the Test Mode or if the manufacturer doesn’t have one, ask your manufacturing partner their preferred way of testing it. As Holder et al conclude in their article,
“The systematic failure of some models to meet EIN standards is both puzzling and troublesome. Either it is the case that the test protocols used by manufacturers are not replicable clinically (making quality control impossible) or a very large portion of hearing aids from specific manufacturers are not meeting quality control standards. It is hard to imagine that either of these outcomes is acceptable to practicing clinicians or the hearing aid industry as a whole.” p 626
Professionals must take pride in being the gatekeeper of quality control. This requires pre-emptive communication with the manufacturer and meticulousness in our testing. “Good audiology” can take a mediocre fitting and make it a better one.
Part 2 will take a deeper dive into measuring EIN in modern hearing aids.
Holder, J, Picou, E., Gruenwald, J & Ricketts, T. (2016) Do modern hearing aids meet the ANSI standard? Journal of the American Academy of Audiology. 27, 619-627.
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 email@example.com or firstname.lastname@example.org.