February 5, 2014 VIA ELECTRONIC SUBMISSION Division of Dockets Management (HFA- 305) Food and Drug Administration 5630 Fishers Lane, Room 1061 Rockville, MD 20852 RE: Bose Corporation Comments Regulatory Requirements for Hearing Aid Devices and Personal Sound Amplification Products: Draft Guidance for Industry and Food and Drug Administration Staff Dear Sir or Madam: Bose Corporation is a U.S.- based company that designs, manufactures and sells electronics and audio equipment worldwide. Bose appreciates this opportunity to comment on the FDA s 2013 Draft Guidance document, which strives to clarify differences between hearing aids (HAs) and personal sound amplification products (PSAPs). We understand the difficulty in achieving this goal, but we believe the proposed guidance requires further revision. Our recommended changes would help the FDA guidance to be better aligned with current understandings of hearing science and with the rapid changes in technology that are occurring now and are sure to continue. One stated goal of the draft guidance is to provide a description of listening situations that are typically associated with and indicative of hearing loss. To this end, the draft specifies a number of situations in which there is an expectation that hearing- impaired individuals will have difficulty understanding speech but normal- hearing listeners will not be impacted. These situations include: (a) difficulty understanding conversations in crowded rooms (b) difficulty listening to another person nearby (c) difficulty listening situations in which environmental noise might interfere with speech intelligibility In assuming that the above situations are difficult solely for individuals with hearing loss, the draft allows only HAs to address these situations. However, everyday experience suggests and the scientific literature indicates that the above situations can be problematic for both normal hearing listeners and individuals with hearing loss. Therefore, the complete exclusion of PSAPs for these uses seems inappropriate. We recommend that the draft guidance be revised to remove these examples (a) (c) above, to recognize that both PSAPs and HAs can address these problems to varying degrees and to allow both PSAPs and HAs to be marketed as appropriate to individuals who might benefit from them.
Draft Guidance Document on PSAPs Page 2 of 10 The rationale for our recommendation is a growing body of results from hearing scientists indicating that not all people who have difficulty understanding speech in such situations have abnormal hearing. Yes, individuals with hearing loss are certainly challenged by many listening environments. But, it is now becoming clear that listeners with clinically normal hearing also vary significantly in their ability to understand speech and, as a result, may be highly challenged in complex listening situations. Such situations include cases like those listed above. The evidence for this is reviewed in the attached Appendix. A key conclusion is that because these variations in understanding occur among individuals with normal hearing (as defined by standard clinical audiometry), other factors must account for these differences in performance. It remains an active area of research to identify the underlying factors at play. Regardless of that uncertainty, there exists a clear need for products that can ameliorate the acoustic consequences of complex environments. They can potentially bring great benefits to many individuals, whether or not they have hearing impairment. We believe that allowing only HAs to address this need is not in the public interest. More broadly, in light of the new understandings about listening difficulties and anticipated progress in technology, we recommend that the FDA invite further stakeholder dialog on new regulatory approaches for distinguishing between medical and non- medical products that help people hear better. For example, perhaps PSAPs could be marketed as a means to improve hearing and listening for the broader populace so long as there are reasonable safeguards to limit potential for harm, such as: 1) PSAPs have limits to prevent excessive amplification that could put one s hearing at risk. 2) PSAPs are sold with a caution notice which the purchaser must view in order to access the product, advising them to consult a physician (or an audiologist) if they notice any marked degradation in their hearing. This is consistent with the waiver that audiologists must collect and retain today, when dispensing HAs. In conclusion, the 2013 Draft Guidance document expands the distance between the problems addressable by HAs and PSAPs. In our view, a different approach is warranted. Modern hearing science informs us that listening can be difficult for many people, not just those with measurable threshold changes. Any new regulatory guidance should incorporate these considerations to enable more individuals to have access to products designed to help them hear better in complex listening environments. Respectfully, Dr. William M. Rabinowitz Manager, Acoustic Research, Bose Corp. bill_rabinowitz@bose.com Daniel M. Gauger Senior Researcher, Bose Corp. dan_gauger@bose.com
Draft Guidance Document on PSAPs Page 3 of 10 Appendix: Research demonstrating deficits among individuals with normal audiometric thresholds Work in three distinct areas is relevant; studies are cited below along with their abstracts or overviews and selected quotes taken directly from them. Area 1: Normal hearing listeners exhibit varying abilities to extract information in complex spatial listening tasks. Ruggles, D, & Shinn- Cunningham, B (2011): Spatial selective auditory attention in the presence of reverberant energy: Individual differences in normal- hearing listeners. J Assoc Research in Otolaryngology, 12, 395-405. Abstract (italics & underlining added): Listeners can selectively attend to a desired target by directing attention to known target source features, such as location or pitch. Reverberation, however, reduces the reliability of the cues that allow a target source to be segregated and selected from a sound mixture. Given this, it is likely that reverberant energy interferes with selective auditory attention. Anecdotal reports suggest that the ability to focus spatial auditory attention degrades even with early aging, yet there is little evidence that middle- aged listeners have behavioral deficits on tasks requiring selective auditory attention. The current study was designed to look for individual differences in selective attention ability and to see if any such differences correlate with age. Normal- hearing adults, ranging in age from 18 to 55 years, were asked to report a stream of digits located directly ahead in a simulated rectangular room. Simultaneous, competing masker digit streams were simulated at locations 15 left and right of center. The level of reverberation was varied to alter task difficulty by interfering with localization cues (increasing localization blur). Overall, performance was best in the anechoic condition and worst in the high- reverberation condition. Listeners nearly always reported a digit from one of the three competing streams, showing that reverberation did not render the digits unintelligible. Importantly, inter- subject differences were extremely large. These differences, however, were not significantly correlated with age, memory span, or hearing status. These results show that listeners with audiometrically normal pure tone thresholds differ in their ability to selectively attend to a desired source, a task important in everyday communication. Further work is necessary to determine if these differences arise from differences in peripheral auditory function or in more central function. Ruggles, D, Bharadwaj, H, & Shinn- Cunningham, B (2011): Normal hearing is not enough to guarantee robust encoding of suprathreshold features important in everyday communication. Proceedings National Academy of Sciences (PNAS), 108(37), 15516-15521. Abstract (italics & underlining added): Normal hearing is typically defined by threshold audibility, even though everyday communication relies on extracting key features of easily audible sound, not on sound
Draft Guidance Document on PSAPs Page 4 of 10 detection. Anecdotally, many normal- hearing listeners report difficulty communicating in settings where there are competing sound sources, but the reasons for such difficulties are debated: Do these difficulties originate from deficits in cognitive processing, or differences in peripheral, sensory encoding? Here we show that listeners with clinically normal thresholds exhibit very large individual differences on a task requiring them to focus spatial selective auditory attention to understand one speech stream when there are similar, competing speech streams coming from other directions. These individual differences in selective auditory attention ability are unrelated to age, reading span (a measure of cognitive function), and minor differences in absolute hearing threshold; however, selective attention ability correlates with the ability to detect simple frequency modulation in a clearly audible tone. Importantly, we also find that selective attention performance correlates with physiological measures of how well the periodic, temporal structure of sounds above the threshold of audibility are encoded in early, subcortical portions of the auditory pathway. These results suggest that the fidelity of early sensory encoding of the temporal structure in suprathreshold sounds influences the ability to communicate in challenging settings. Tests like these may help tease apart how peripheral and central deficits contribute to communication impairments, ultimately leading to new approaches to combat the social isolation that often ensues. Quote (italics & underlining added): Our results shed light on the importance of peripheral auditory coding for auditory perception in all types of complex social settings, from the boardroom to the football field. Individuals with poorer peripheral encoding may struggle to communicate or even withdraw entirely in such settings. Such listeners are likely to be particularly vulnerable when faced with everyday challenges that listeners with more robust auditory peripheral encoding can handle relatively gradually, from listening in reverberant or noisy rooms to dealing with the normal effects of aging on auditory processing. Shamma, SA (2011): Hearing impairments hidden in normal listeners. Proceedings National Academy Sciences (PNAS), 108(37), 16139-16140. This paper is a commentary on the previous study (Ruggles et al., 2011). It also provides analysis of putative physiological mechanisms, beyond hearing loss for tones, which might be operative in these listening tasks. It concludes (italics & underlining added): Finally, as the authors point out, the societal implications of better auditory screening are substantial because it makes apparent the dangers of pervasive habits such as listening to blaring music and living with loud environmental sounds, all the while hiding behind the false security of normal audiometric thresholds!
Draft Guidance Document on PSAPs Page 5 of 10 Area 2: Aging impacts speech perception and particularly listening in noise beyond the effects of hearing loss for tones Anderson, S, Parbery- Clark, A, Yi, H- G, & Kraus, N (2011): A neural basis of speech- in- noise perception in older adults. Ear & Hearing, 32(6), 750-757. Overview (italics & underlining added): Objective: We investigated a neural basis of speech- in- noise perception in older adults. Hearing loss, the third most common chronic condition in older adults, is most often manifested by difficulty understanding speech in background noise. This trouble with understanding speech in noise, which occurs even in individuals who have normal- hearing thresholds, may arise, in part, from age- related declines in central auditory processing of the temporal and spectral components of speech. We hypothesized that older adults with poorer speech- in- noise (SIN) perception demonstrate impairments in the subcortical representation of speech. Design: In all participants (28 adults, age 60 73 yr), average hearing thresholds calculated from 500 to 4000 Hz were < 25 db HL. The participants were evaluated behaviorally with the Hearing in Noise Test (HINT) and neurophysiologically using speech- evoked auditory brainstem responses recorded in quiet and in background noise. The participants were divided based on their HINT scores into top and bottom performing groups that were matched for audiometric thresholds and intelligent quotient. We compared brainstem responses in the two groups, specifically, the average spectral magnitudes of the neural response and the degree to which background noise affected response morphology. Results: In the quiet condition, the bottom SIN group had reduced neural representation of the fundamental frequency of the speech stimulus and an overall reduction in response magnitude. In the noise condition, the bottom SIN group demonstrated greater disruption in noise, reflecting reduction in neural synchrony. The role of brainstem timing is particularly evident in the strong relationship between SIN perception and quiet- to- noise response correlations. All physiologic measures correlated with SIN perception. Conclusion: Adults in the bottom SIN group differed from the audiometrically matched top SIN group in how speech was neurally encoded. The strength of subcortical encoding of the fundamental frequency appears to be a factor in successful speech- in- noise perception in older adults. Given the limitations of amplification, our results suggest the need for inclusion of auditory training to strengthen central auditory processing in older adults with SIN perception difficulties. Quote (italics & underlining added): Older adults frequently report having difficulty understanding speech in background noise. Peripheral hearing loss explains some of this difficulty Yet, speech- in- noise (SIN) perception difficulty can be present in older adults who have normal audiometric thresholds The audiogram fails to predict to accurately predict speech recognition performance for all age groups, particularly in background noise The factors contributing to SIN perception difficulties
Draft Guidance Document on PSAPs Page 6 of 10 are not well understood. Deficits in cognitive processing contribute to the problems in older adults when listening in noise. Anderson, S, White- Schwoch, T, Parbery- Clark, A, & Kraus, N (2013): A dynamic auditory- cognitive system supports speech- in- noise perception in older adults. Hearing Research, 300, 18-32. Abstract (italics & underlining added): Understanding speech in noise is one of the most complex activities encountered in everyday life, relying on peripheral hearing, central auditory processing, and cognition. These abilities decline with age, and so older adults are often frustrated by a reduced ability to communicate effectively in noisy environments. Many studies have examined these factors independently; in the last decade, however, the idea of an auditory- cognitive system has emerged, recognizing the need to consider the processing of complex sounds in the context of dynamic neural circuits. Here, we used structural equation modeling to evaluate the interacting contributions of peripheral hearing, central processing, cognitive ability, and life experiences to understanding speech in noise. We recruited 120 older adults (ages 55 79) and evaluated their peripheral hearing status, cognitive skills, and central processing. We also collected demographic measures of life experiences, such as physical activity, intellectual engagement, and musical training. In our model, central processing and cognitive function predicted a significant proportion of variance in the ability to understand speech in noise. To a lesser extent, life experience predicted hearing- in- noise ability through modulation of brainstem function. Peripheral hearing levels did not significantly contribute to the model. Previous musical experience modulated the relative contributions of cognitive ability and lifestyle factors to hearing in noise. Our models demonstrate the complex interactions required to hear in noise and the importance of targeting cognitive function, lifestyle, and central auditory processing in the management of individuals who are having difficulty hearing in noise. Desjardins, JL, & Doherty, KA (2013): Age- related changes in listening effort for various types of masker noises. Ear & Hearing, 34(1), 261-272. Overview (italics & underlining added): Objective: The purpose of the present study was to evaluate the relationship between cognitive function, listening effort, and speech recognition for a group of younger and older adults with normal hearing and a group of older adults with hearing impairment in various types of background maskers. The authors hypothesize that, as the masker condition becomes more difficult listening effort will increase, but the increase will be greater for older participants than for younger participants. Design: A dual- task paradigm was used to objectively evaluate listening effort. The primary task required participants to repeat sentences presented in three different background- masker conditions: (1) two- talker (TT), (2) six- talker, and (3) speech- shaped noise (SSN). The secondary task was a Digital Visual Pursuit Rotor Tracking test, for which participants were instructed to
Draft Guidance Document on PSAPs Page 7 of 10 use a computer mouse to track a moving target around an ellipse that was displayed on a computer screen. Each of the two tasks was separately and concurrently presented at a fixed overall speech- recognition performance level of 76% correct. In addition, participants subjectively rated how easy it was to listen to the sentences in each masker condition on a scale from 0 (i.e., very difficult) to 100 (i.e., very easy). Last, participants completed a battery of cognitive tests that measured working memory (Reading Span Test), processing speed (Digit Symbol Substitution Test), and selective attention (Stroop Test) ability. Results: Results revealed that participants working memory and processing speed abilities were significantly related to their speech- recognition performance in noise in all three background- masker conditions. Participants rated the TT condition to be the most difficult listening condition and the SSN condition to be the easiest listening condition. Both groups of older participants (sic: both those without and with hearing loss) expended significantly more listening effort than younger participants did in the SSN and TT (sic: speech- shaped noise and two- talker) masker conditions. For each group of participants, there were no significant differences in listening effort measured across the masker conditions, with the exception of the younger participants, who expended more effort listening in the six- talker masker condition compared with the SSN condition. Participants listening effort expended on the TT and SSN masker conditions was significantly correlated with their working memory and processing speed performance. Conclusions: Findings from the present study indicate that older adults require more cognitive resources than younger adults to understand speech in background noise. Krull, V, Humes, LE, & Kidd, GR (2013): Reconstructing whole from parts: Effects of modality, age, and hearing loss on word recognition. Ear & Hearing, 134(2), c14- c23. Overview (italics & underlining added): Objective: In this study, the effects of age, hearing loss, and modality on the ability to integrate partial information in degraded stimuli, either speech or text, were examined using isolated words. It was hypothesized that the ability to make use of partial information in speech diminishes with age. It was also hypothesized that additional contributions of cochlear pathology underlying hearing loss would be manifest as a further decrement in performance for older adults with hearing loss, relative to older adults with normal hearing. Furthermore, it was hypothesized that, if the ability to integrate partial information in speech is amodal, then recognition performance for degraded speech would be associated with recognition performance for parallel measures of degraded text. Last, it was hypothesized that, if the nature of the amodal ability to integrate partial information is cognitive, then the performance on auditory and visual measures of word recognition would be correlated with performance on measures of working memory. Design: Twenty- five young adults with normal hearing, 20 older adults with normal hearing, and 21 older adults with hearing loss participated in this study. All participants completed three auditory and two parallel visual tasks consisting of listening to or reading degraded words or text. Older participants also completed a working- memory test battery. Group effects were
Draft Guidance Document on PSAPs Page 8 of 10 examined for each of the auditory and visual measures. Performance of older participants on cognitive measures was compared with available data from a younger group participating in a different study in our laboratory (with similar protocol). Correlations between auditory and visual measures of speech recognition were examined for all participants. In addition, correlations between perceptual and cognitive measures were computed for the older participants. Finally, the relationship between dependent auditory measures and other independent measures in older adults were further examined using stepwise linear regression analyses. Results: Of the 10 possible comparisons between the young and the two older groups for the five primary dependent measures, the young performed significantly better than the elderly did, 8 of the 10 times. The two older groups performed similarly for most tasks. In young adults, performance among the auditory tasks and between the two visual tasks was significantly and moderately to strongly correlated. In addition, performance on one of the visual tasks was weakly to moderately significantly correlated with performance on each of the three auditory tasks. Similar moderate to strong correlations were found within the auditory and visual modalities in older adults. However, none of the between- modality correlations were significant in the elderly. Conclusions: In summary, the results of this study suggest that the ability to integrate partial information in degraded words diminishes with age. Once audibility is accounted for, this ability does not seem to diminish with cochlear pathology. In young adults, both modality specific factors and amodal cognitive factors seem to contribute to this ability. In older adults, although modality- specific factors continue to be important, it seems that the perceptual mechanisms that underlie the processing of degraded speech and text are separate, at least for isolated words. Our results suggest that, when peripheral factors are accounted for, some higher- level, yet- to- be identified, age- related factors contribute to speech- communication difficulties in the elderly. Quotes from the final summary (italics & underlining added): In summary, our results suggest that the ability to make use of partial information in degraded speech diminishes with age, at least for isolated words. The present results show an age- related decrease which cannot be accounted for by reductions in audibility or a decrease in working memory capacity. Our results suggest that, when peripheral factors are accounted for, some higher- level, yet- to- be identified age- related factors contribute to speech- communication difficulties in the elderly.
Draft Guidance Document on PSAPs Page 9 of 10 Area 3: Normal hearing for tones does not indicate normal suprathreshold hearing function Charlie Liberman s group has recently shown in animals that noise exposure causing only temporary hearing loss and no permanent changes in hearing threshold can produce substantial reductions in suprathreshold physiological responses of the inner ear. Thus, normal audiometric thresholds may not detect underlying damage that could be responsible for suprathreshold listening variations. Kujawa, SG, & Liberman, MC (2009): Adding insult to injury: Cochlear nerve degeneration after temporary noise- induced hearing loss. J Neuroscience, 29, 14077-14085. Abstract (italics & underlining added): Overexposure to intense sound can cause temporary or permanent hearing loss. Postexposure recovery of threshold sensitivity has been assumed to indicate reversal of damage to delicate mechano- sensory and neural structures of the inner ear and no persistent or delayed conse- quences for auditory function. Here, we show, using cochlear functional assays and confocal imaging of the inner ear in mouse, that acoustic overexposures causing moderate, but completely reversible, threshold elevation leave cochlear sensory cells intact, but cause acute loss of afferent nerve terminals and delayed degeneration of the cochlear nerve. Results suggest that noise- induced damage to the ear has progressive consequences that are considerably more widespread than are revealed by conventional threshold testing. This primary neuro- degeneration should add to difficulties hearing in noisy environments, and could contribute to tinnitus, hyperacusis, and other perceptual anomalies commonly associated with inner ear damage. Quote (italics & underlining added): It is sobering to consider that normal threshold sensitivity can mask ongoing and dramatic neural degeneration in noise- exposed ears, yet threshold sensitivity represents the gold standard for quantifying noise damage in humans. Federal exposure guidelines (OSHA, 1974; NIOSH, 1998) aim to protect against permanent threshold shifts, an approach that assumes that reversible threshold shifts are associated with benign levels of exposure. Moreover, lack of delayed threshold shifts after noise has been taken as evidence that delayed effects of noise do not occur (Humes et al., 2005). The present results contradict these fundamental assumptions by showing that reversibility of noise- induced threshold shifts masks progressive underlying neuropathology that likely has profound long- term consequences on auditory processing. Furman, AC, Kujawa, SG, & Liberman, MC (2013): Noise- induced cochlear neuropathy is selective for fibers with low spontaneous rates. J Neurophysiology, 110, 577-586. Abstract (italics & underlining added): Acoustic overexposure can cause a permanent loss of auditory nerve fibers without destroying cochlear sensory cells, despite complete recovery of cochlear thresholds (Kujawa and Liberman
Draft Guidance Document on PSAPs Page 10 of 10 2009), as measured by gross neural potentials such as the auditory brainstem response (ABR). To address this nominal paradox, we recorded responses from single auditory nerve fibers in guinea pigs exposed to this type of neuropathic noise (4- to 8- khz octave band at 106 db SPL for 2 h). Two weeks postexposure, ABR thresholds had recovered to normal, while suprathreshold ABR amplitudes were reduced. Both thresholds and amplitudes of distortion- product otoacoustic emissions fully recovered, suggesting recovery of hair cell function. Loss of up to 30% of auditory- nerve synapses on inner hair cells was confirmed by confocal analysis of the cochlear sensory epithelium immunostained for pre- and postsynaptic markers. In single fiber recordings, at 2 week postexposure, frequency tuning, dynamic range, postonset adaptation, first- spike latency and its variance, and other basic properties of auditory nerve response were all completely normal in the remaining fibers. The only physiological abnormality was a change in population statistics suggesting a selective loss of fibers with low- and medium- spontaneous rates. Selective loss of these high threshold fibers would explain how ABR thresholds can recover despite such significant noise- induced neuropathy. A selective loss of high- threshold fibers may contribute to the problems of hearing in noisy environments that characterize the aging auditory system.