ADA Statement: FDA OTC Hearing Aid Proposed Rule Provisions for Maximum Sound Output and Gain

Stephanie Czuhajewski, MPH, CAE, Executive Director

February 1, 2022

I. THE BIG PICTURE
Following the release of the Food and Drug Administration (FDA) Over-the Counter (OTC) Hearing Aid Proposed Rule (Proposed Rule) in October 2021,¹ the Academy of Doctors of Audiology (ADA) convened an internal task force for the purpose of evaluating whether the Proposed Rule (i) meets the statutory requirements outlined in FDARA (FDA Reauthorization Act) and (ii) supports evidence-based practices, professional autonomy, consumer access, and competition.

During this process, the ADA OTC task force conducted a comprehensive literary review of scientific presentations, research articles, the President’s Council of Advisors on Science and Technology (PCAST) report (2015)² and National Academy of Science Engineering and Medicine (NASEM) Report (2016)³, FDA regulations, ANSI standards, and the “Regulatory Recommendations for OTC Hearing Aids: Safety & Effectiveness” (2018 Consensus Paper)⁴ to assess the Proposed Rule provisions for technical and performance standards for OTC hearing aids.

ADA advocates for public policies that improve consumer access to audiology services and access to safe, effective, and affordable treatments for hearing loss, including OTC hearing aids. ADA believes that through the evaluation of science and the application of the information found, consumers and the profession of audiology will be best served by a legal framework that is evidence-based.

After a careful evaluation of the evidence, the ADA OTC task force and the ADA Board of Directors concluded the original methodologies used to justify the 25 dB (decibel) gain limit and the 110 dB output limit in the 2018 Consensus Paper—published as a consensus paper from several hearing healthcare organizations, including ADA—was flawed. In January 2022, ADA subsequently submitted the following recommendations to the FDA:

• ADA supports FDA’s proposal to allow an output limit up to 120 dB OSPL90 for OTC hearingaids with input-controlled compression and user adjustable volume control.
• ADA urges the FDA to implement a general output limit for OTC hearing aids of 110 dB OSPL90 when the hearing aid does not include input-controlled compression and user adjustable volume
• ADA supports FDA’s proposal to forgo gain limitations for OTC hearing

ADA continues to endorse several portions of the recommendations contained in the 2018 Consensus Paper’s five major areas. However, after a renewed and objective review, ADA maintains strong concerns and no longer agrees with two specific recommendations.

ADA does not support the 2018 Consensus Paper recommendations regarding maximum gain and maximum output:

• The 2018 Consensus Paper working group recommended a high-frequency average full on gain (HFA-FOG) limit of 25 dB as defined for measurement in a 2cc coupler, with an input level of 50 dB SPL per ANSI standard S3.22-2014.
• The 2018 Consensus Paper working group recommended a peak (or maximum) 2cc coupler OSPL90, per ANSI S3.22-2014, not to exceed 110 dB SPL.

Furthermore, ADA remains committed to collaborating with other professional organizations to ensure that federal and state laws for OTC hearing aids are implemented responsibly, transparently, and in a manner that maximizes consumer access to audiology services.

II. THE TIMELINE

A multi-organization opinion paper, “Regulatory Recommendations for OTC Hearing Aids: Safety & Effectiveness,” was released in August 2018 (2018 Consensus Paper). This 2018 Consensus Paper is a 35-page document from three associations representing audiologists (ADA, the American Academy of Audiology (AAA), and the American Speech-Language-Hearing Association (ASHA)), and one association representing hearing instrument specialists, the International Hearing Society (IHS). While the hearing aid industry trade association, Hearing Industries Association (HIA) was not credited with authorship, several employees of their member companies (i.e., industry personnel) were included in the 2018 Consensus Paper working group and HIA immediately endorsed the paper upon release.

Throughout the development of the 2018 Consensus Paper, there was strong debate among participating organizations regarding recommendations for maximum sound pressure level (SPL) output and gain. Despite best efforts to align on assumptions, evidence, and a rationale supporting one recommendation or another, in the end, every organization, including ADA, made concessions to arrive at the 110 dB SPL (output) and 25 dB (gain) recommendations.

The 2018 Consensus Paper had five key recommendations to the FDA regarding OTC hearing aids:

1. Establish product requirements appropriate for OTC hearing devices targeting mild-to- moderate hearing impairment.
2. Define concise, out-of-the box labeling appropriate for OTC, with strong recommendation to consult with a hearing health care professional.
3. Define comprehensive, inside-the-box labeling appropriate forover-the- counter medical devices.
4. Define the new OTC category so that it is easily comprehensible by consumers and in line with risk class requirements for safety and effectiveness.
5. Adequate provisions for consumer protection, in coordination with the Federal Trade Commission (FTC).
6. ADA was pleased that the FDA addressed all five areas in the 2021 OTC Hearing Aid Proposed Rule.

The 2018 Consensus Paper provided a valuable “strawman” framework for regulators to consider as they implement the OTC Hearing Aid Act (a subsection of FDARA, the FDA Reauthorization Act of 2017). The conclusions drawn, however, were simply an amalgamation of the positions and opinions supported by selected evidence put forward by the authoring organizations and other stakeholders, including the Hearing Industries Association (HIA), and should not be confused with or portrayed as a peer-reviewed research publication.

Following the release of the FDA OTC Hearing Aid Proposed Rule in October 2021, ADA convened an internal task force for the purpose of evaluating whether the Proposed Rule meets the statutory requirements outlined in FDARA and supports evidence-based practices, professional autonomy, consumer access, and competition.

During this process, the ADA OTC task force conducted a comprehensive literary review of scientific presentations, research articles, the PCAST report, the NASEM report, FDA regulations, ANSI standards, and the 2018 Consensus Paper to assess the Proposed Rule provisions for technical and performance standards for OTC hearing aids.

In a meeting of representatives from AAA, ADA, ASHA, IHS, HIA, and the American Academy of Otolaryngology-Head Neck Surgery (AAO-HNS), and the Hearing Loss Association of America (HLAA) (2021, December 2), the question was put forward to all organizations as to whether all organizations would use the 2018 Consensus Paper as an agreed-upon starting point for harmonizing comments on the FDA OTC Hearing Aid Proposed Rule. At that time, ADA notified the other organizations that ADA was not prepared to do so without first completing the full review by its own task force.

Following the completion of the work by the ADA task force, ADA held a member town hall webinar (2022, January 12) on “Analysis of FDA Proposed OTC HA Rule.” Here, ADA presented a scientifically supported response to the request from the FDA for comments on the proposed rule, including some positions that differed from the 2018 Consensus Paper.

Specifically, ADA does not support the 2018 Consensus Paper recommendations regarding maximum gain and maximum output.

• The 2018 Consensus Paper working group recommended a high frequency average full-on gain (HFA-FOG) limit of 25 dB as defined for measurement in a 2cc coupler, with an input level of 50 dB SPL per ANSI standard S3.22-2014.
• The 2018 Consensus Paper working group recommended a peak (or maximum) 2cc coupler OSPL90, per ANSI S3.22-2014, not to exceed 110 dB SPL.

After a thorough review of the science related to electroacoustic performance, ADA concluded that the original methodologies used to justify the 25 dB gain limit and the 110 dB output limit in the 2018 Consensus Paper was incomplete. In January 2022, ADA submitted the following recommendations to the FDA:

• ADA supports FDA’s proposal to allow an output limit up to 120 dB OSPL90 for OTC hearingaids with input-controlled compression and user adjustable volume control.
• ADA urges the FDA to implement a general output limit for OTC hearing aids of 110 dB OSPL90 where the hearing aid does not include input-controlled compression and user adjustable volume
• ADA supports FDA’s proposal to forgo gain limitations for OTC hearing aids and notes that this was not a statutory requirement under FDARA.

Following the member town hall webinar, ADA received immediate and strong written (2022, January 14, enclosed) and oral (2022, January 17) criticism from representatives of the hearing aid industry regarding ADA’s revised position on the 2018 Consensus Paper. In the January 17, 2022, virtual meeting with industry representatives, in which multiple issues were discussed, it was explained by the industry representatives that ADA’s continued endorsement of the 2018 Consensus Paper recommendations (with lower limits on gain and output) was important to support the “traditional hearing aid business to … remain the traditional hearing aid business.” ADA views the Over-the-Counter Hearing Aid Act of 2017 as an opportunity to improve on the traditional hearing aid business and ADA supports new methods to increase access to hearing care services and affordability of hearing devices.

III THE DETAILS

ADA diverges from the 2018 Consensus Paper on the gain and output recommendations as follows:

Comments on “Definition of intended users for OTC hearing devices” (pp 4-7 of the 2018 Consensus Paper):

• The OTC Hearing Aid Act of 2017 covers hearing devices “intended to be used by adults aged 18 and older to compensate for perceived mild to moderate hearing impairment" (page 4). The 2018 Consensus Paper states that “older individuals tend to underestimate their hearing loss” (page 6). The combination of these two statements is that a person with a perceived mild-to-moderate hearing loss may also be in the audiometry confirmed category of what many, but not all, American audiologists would term “moderately-severe hearing” loss of up to 70 dB HL. This issue is addressed in the section “Unintended but foreseeable users” (page 7) where it is stated “Considering that this will be sold over-the-counter, this group may include adults who perceive they … have a more severe hearing impairment (56 dB HL or higher).” ADA agrees that these are foreseeable users but disagrees that these are unintended users. The legislation expressly states that the devices are for user- perception of mild-to-moderate hearing loss and does not state the devices are for users with ≤ 55 dB HL hearing loss.
• A second point is whether to use any concrete number, or what number, for degree of hearing loss, when intended users have “perceived” hearing loss. The selection of a flat 55 dB HL hearing loss (page 5) as the designation of maximum degree of hearing loss that is applicable for OTC hearing aids is controversial, as many audiologists, organizations, hearing aid and cochlear implant manufacturers categorize moderate hearing loss up to 60 dB HL or 70 dB HL. This conversation was further complicated when the FDA, in their 2021, December 7 webinar on OTC hearing aids, displayed an audiogram categorizing moderate hearing loss up to 70 dB HL. Selecting 70 dB HL hearing thresholds as the limit of “moderate” hearing sensitivity are consistent with a global view of “moderate” hearing loss but are inconsistent with some US-oriented audiometry classification systems where hearing threshold responses consistent with of 56 – 70 dB HL are referred to as “moderately-severe.”

In summary, ADA does not propose that perceived mild-to-moderate hearing loss be defined as 55 dB HL, 60 dB HL, 70 dB HL, or indeed any audiometry-confirmed level. ADA submits that using any audiometry- defined limit moves away from “perceived” as an inseparable part of the candidacy criteria and is inconsistent with the congressional intent of the legislation. A generalized definition that promotes discussions on gain and output limits would lead to flexible recommendations, and ADA believes this would be consistent with the Congressional intent of the OTC Hearing Aid Act of 2017.

Comments on “Gain requirements” (pp 7-11)

• ADA has objections to the underlying assumptions used to determine the maximum gain limits for a 55 dB HL hearing loss. The assumptions include binaural usage by new users to amplification as one example (page 9). These assumptions exclude monaural users, experienced users, and users with any type of hearing loss other than sensorineural. These exclusions are highly questionable as the assumptions could have easily included monaural, experienced users, and users who may have mixed or conductive hearing loss that does not require medical intervention.
  
  The real-world impact of the modeling decisions of 55 dB HL hearing loss and only binaural, new users with sensorineural hearing loss is an inappropriate limitation on the maximum permissible gain limit to 25 dB HFA FOG for OTC hearing aid fittings, thereby reducing the number of potential users with hearing impairment who would benefit from an OTC device. An example of the consequences of these exclusionary assumptions can be seen in Table 1 (page 9), where a monaural, experienced hearing aid user with 55 dB HL thresholds is prescribed 30.1 dB HFA FOG using the National Acoustic Laboratories, Non-Linear Revision 2 prescriptive fitting rationale (NAL-NL2),⁵ the most common method of fitting prescription hearing aids in the United States.
  
  If the 25 dB HFA FOG recommendation is implemented by the FDA, this individual with a moderate, sensorineural hearing loss would only be able to have their amplification needs met with a prescription hearing aid. This is a clear example of where the 2018 Consensus Paper does not meet the congressional intent of the OTC Hearing Aid Act of 2017 by conflating concerns over safety with a demonstrable impact on effectiveness.

• ADA further considered the algorithmic analysis referenced in the 2018 Consensus Paper regarding a mathematical model using the NAL-NL2 prescriptive use-gain target. The use-gain targets were translated into a 2cc coupler HFA FOG values, serving as the proxy for a maximum gain limit. This procedure ignores the clinical mandate that hearing aids are not to be fit or worn at the maximum setting, or full-on gain (FOG).
  
  Hearing aids should be fit to user gain targets and have reserve gain available so the device user can increase the volume (gain) when they desire to hear sounds of low intensity (soft sounds). A typical amount of reserve gain in hearing aid fittings is greater than or equal to 5 dB but less than or equal to 10 dB. The lack of accounting for reserve gain means that the effective performance limit of these devices will be less than or equal to 20 dB HFA FOG, not the intended 25 dB HFA FOG. Devices with usable gain of less than or equal to 20 dB are appropriate for persons with mild hearing loss and will meet the needs of some, but not all, individuals with moderate hearing loss. This is another clear example of where the 2018 Consensus Paper does not meet the Congressional intent of the OTC Hearing Aid Act of 2017.

In summary, ADA does not support the 2018 Consensus Paper use of exclusion criteria, based on assumptions from most-common device usage for determining a gain limit. Instead, ADA supports using an inclusion criterion that would account for all intended device usage. As such, ADA supports FDA taking a more flexible position insofar as gain limitations may negatively impact competition and innovation for new OTC devices. A low gain limit, as was recommended in the 2018 Consensus Paper, would reduce device effectiveness for the large population of individuals who could benefit from OTC devices, is not a statutory requirement under FDARA, and is inconsistent with the Congressional intent of the Over-the- Counter Hearing Aid Act of 2017.

Comments on “Maximum Power Output Limitation” (pp 11-17)

• ADA maintains the 2018 consensus document misconstrues the relationship between the maximum output for any single pure tone and that for a broadband signal. In the 2018 Consensus Paper, it was written (pp. 15-16):
  
  “… when a broadband signal (such as speech or music that includes energy over a broad range of frequencies) is presented to the hearing aid, the output of the hearing aid is the sum of the energy at all the frequencies. Indeed, the maximum output of the hearing aid will be limited by the peak OSPL90 at each frequency but summed across all the frequencies of interest. Thus, a sinusoid or a very narrow band of noise of the same spectral level presented at a 90 dB SPL level may have an overall output closely related to the value of the peak OSPL90. However, a broadband signal (such as speech or music) of the same spectral level at all frequencies will have an overall output level far exceeding the value of the peak OSPL90.”
  
  This conclusion is not accurate. Broadband signals can be output from the hearing aid only at average (e.g., root-mean-square or RMS) levels that will be well below the OSPL90 value. Even if care is not taken to prevent peak clipping distortion, output from the hearing aid will still not exceed OSPL90.

• ADA has another criticism of the 2018 Consensus Paper justifying the 110 dB OPL90 value from the Johnson paper. In the Introduction to his paper, Johnson writes “MPO levels have two basic uses. One use is to limit the amount of intermittent, short duration sounds to levels below those that are uncomfortable for the wearer. The other purpose is to limit the amount of amplification to higher level inputs occurring more consistently over a long duration (e.g., > 8 hours). This second use was the perspective taken by the study.” ^7,8,9 (page 830)
  
  First, Johnson’s line of reasoning is endorsed in the 2018 Consensus Paper (page 13).
  
  “The proper adjustment of maximum output is the critical parameter that serves the purpose to limit the output of:
  • Intermittent, short duration sounds, to levels that are neither damaging nor uncomfortable to the wearer, and
  • Overamplification of higher level inputs occurring more consistently over a longer duration (e.g. over six-eight hours).”

To determine a hypothetical peak SPL value (appropriate to create an OSPL90 value), both the first point (intermittent, short duration sounds) and the second point (long duration sounds) must be considered. The 111 dB SPL (RMS) is only the long duration value for speech. Johnson addresses this issue and cautions that “The safe output SPL in Table 1 are RMS levels so that peak levels 15 dB higher could be allowed to preserve the sound quality of incoming speech inputs so as not to clip the speech and perhaps allow higher peak levels for other inputs like music." This second factor discussed by Johnson (2017) is not considered in the 2018 Consensus Paper. If it had been, the result would have been far above 110 and closer to 120 dB.

ADA agrees with Bose Corporation in its FDA comments, “…real-world signals are dynamic, unlike steady tones. Speech at a constant level has a crest factor (dB ratio of instantaneous peak to RMS level) of about 15 versus that of 3 dB for a tone.¹⁰ Music often has crest factors that are even higher.¹¹ These crest factor differences (re: a tone) correspondingly decrease the highest level that these signals can be played without distortion (from clipping) and consequent poor sound quality. Therefore, due to the frequency dependence of OSPL90 and the above crest factors, an OSPL90 limit of 120 dB SPL will allow actual speech (and music) to be played only up to around 105 dB SPL. While listening at such levels is not common, it does occur occasionally, and the proposed OSPL90 limits of 115/120 dB SPL are needed to ensure there is adequate headroom for undistorted outputs in these situations.”

In summary, on the issue of maximum output power limitation, ADA does not support several statements, assumptions, and rationales that led to a recommendation for a hard limit of 110 dB OSPL90 for OTC hearing aids. ADA supports the more flexible FDA position with an allowance of 120 dB OSPL90 to promote device efficacy including sound fidelity, when combined with user-controlled methods to lower device output, promoting device safety.

IV. CONCLUDING COMMENT

ADA has been heavily criticized for changing its position regarding key recommendations contained in the collaborative 2018 Consensus Paper. ADA must, however, prioritize accuracy over unity. Promoting and advancing the autonomous practice of audiology, guided by evidence-based practices, requires an adherence to scientific principles that withstands social pressure. A regulatory framework, built upon independently verifiable scientific methods and the earnest application of the evidence found, will deliver accessible, affordable, effective, and safe OTC hearing aids to consumers with hearing loss. ADA welcomes constructive discussion on this issue and maintains that the best way to advance the profession of audiology is by prioritizing the needs of those we serve.

References

1. https://www.govinfo.gov/content/pkg/FR-2021-10-20/pdf/2021-22473.pdf
2. https://obamawhitehouse.archives.gov/sites/default/files/microsites/ostp/PCAST/pcast_hearing_tech_letterreport_final.pdf
3. Hearing Health Care for Adults: Priorities for Improving Access and Affordability: https://www.nationalacademies.org/our- work/accessible-and-affordable-hearing-health-care-for-adults
4. Regulatory Recommendations for OTC Hearing Aids: Safety & Effectiveness, Consensus Paper from Hearing Care Associations, August 14, 2018. https://hearinghealthmatters.org/hearingnewswatch/2018/consensus-otc-hearing-aid-classification/
5. Keidser, G., Dillon, H., Flax, M., Ching, T., & Brewer, S. (2011). The NAL-NL2 prescription procedure. Audiology Research, 1(1), e24. https://doi.org/10.3390/audiores.2011.25
6. Johnson, E. (2017). Safety limit warning levels for the avoidance of excessive sound amplification to protect against further hearing loss, International Journal of Audiology, 56: 829-836.
7. The Occupational Safety Health Administration (OSHA) and National Institute for Occupational Safety & Health (NIOSH) limits for exposure are applicable only to industrial noise in a sound field for age-adjusted normal hearing persons. For these occupational standards to be applicable to hearing aids, in-ear (ear drum referenced) levels would have to be diffuse field referred and then adjusted for the hearing loss.
8. https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.95
9. https://www.cdc.gov/niosh/docs/98-126/pdfs/98-126.pdf?id=10.26616/NIOSHPUB98126
10. American National Standards Institute (2020). ANSI S3.5-1997 (R2020). Methods for the Calculation of the Speech Intelligibility Index. New York: Acoustical Society of America.
11. Chasin, M. (2003). Music and hearing aids. The Hearing Journal, 56(7), 36-41.