補聴器装用時域値をもとにした補聴器のフィッティング法（ＤＲＦ‐ＳＳＭ法）の開発

When fitting hearing aids, there are three guidelines that should always be followed by the dispenser: restore audibility; so that the amplified sound is above the user's threshold, limit the output; so that the amplified signal does not exceed the user's discomfort level, and do no harm; so that the amplified signal is not unintentionally or undesirably altered by the hearing aid. The first two of these three guidelines are obvious. The first is to present sounds above the user's threshold of hearing in order to create an acoustic environment with the maximum amount of audible speech cues. The second ensures that discomfort level is not exceeded, so that the user does not wince or remove the hearing aids when loud sounds are present. The third guideline—do no harm—is less obvious. This indicates that it is important that the hearing aids produce no alteration of the signal other than that which the fitter intends. This is a subtle way of saying that, among other things, well-fitted hearing aids should not distort the desired sound. The topic of distortion is the subject of this issue of Trends in Amplification. The intention of this issue is to explain why distortion occurs in some hearing aids; to explain how distortion is measured; to summarize what can be done to prevent distortion; and to summarize the perception of distortion by the hearing aid wearer. Distortion in hearing aids can be broadly defined as the generation of undesired audible components that are present in the output, but which are not present in the input. When distortion occurs, hearing aids produce undesired elements at the output through the interaction of the processed signal with some internal non-linear mechanism. These undesired components may interfere to some degree or other with the reception of sound by the listener. If these added elements are small compared to the overall signal level, they may effectively cause no interference at all. If they are large, they can be so disruptive to the listener that the desired sound becomes irritating or even incomprehensible. All audio systems inevitably contain some amount of distortion. The practical problem for the listener is the type of distortion that is present and the level that is acceptable or tolerable in hearing aids before the distortion becomes disruptive to speech intelligibility and sound quality. It is known that highly distorted speech in quiet can remain intelligible (Licklider, 1946); however, as dispensers often experience, intelligibility is not the only measure of whether or not a user will accept and wear hearing aids. Gabrielsson and Sjogren (1979b) have shown that overall perceived sound quality is important to users when selecting a hearing aid. Punch (1978) has shown that listeners with mild to moderate sensorineural hearing losses retain the same ability to make distinctions in sound quality judgments as listeners with normal hearing. This implies that good sound quality is as equally important and desired by listeners with a hearing impairment as it is for listeners with normal hearing. Three characteristics of distortion in hearing aids modify the sound delivered to the user: the type of distortion, the relative amount of distortion at different frequencies, and the variation of distortion with different input levels. Since the most important goal for fitting hearing aids is to restore or facilitate communication ability, undistorted sound is important for optimum speech intelligibility and sound quality. However, it is important to also recognize that there are other reasons to provide undistorted amplification of sound. For example, undistorted and pleasant reproduction of music may be an important sensory experience for some listeners. This issue concentrates on different types of undesired modification to the waveshape of the sound, primarily by total harmonic distortion (THD) and intermodulation distortion (IMD). However, in a more general sense, any undesired component added to the sound by hearing aids is a form of distortion. Thus, this issue also discusses sound generated by hearing aids with no signal present at the microphone. This artifact is more commonly called internal noise. Internal noise fits within the definition of distortion given earlier, since internal noise is an undesired product generated in the output of hearing aids that is not present at the input. In some cases, distortion and internal noise are so closely linked that they cannot always be separated into discrete entities. For example, instability in the frequency and shape of the clock pulses in a Class D output stage (often loosely called clock jitter) results in distortion of the signal. However, this artifact may be audibly revealed in the output sound primarily as noise, rather than as distortion of the waveform. According to this broad definition of distortion, undesired noises such as “motorboating” and other acoustic feedback oscillations can also be considered to be forms of distortion. However, acoustic feedback and other similar audible artifacts occurring within hearing aids will not be discussed here. These types of distortion have been discussed in detail by Agnew (1996b) in a previous issue of Trends in Amplification. In this issue distortion is discussed in two general categories: Undesired modification of the waveform of the incoming sound by some mechanism occurring within the hearing aids. The severity of this effect may or may not vary with the acoustic level of the incoming sound. This type of audible artifact is generally what most dispensers refer to as “distortion”. This will be the subject of Part I of this issue, and will follow the definition used for distortion in this text. The production of undesired audible components in the output sound, regardless of whether or not there is any acoustic input to the hearing aid. This is generally called “noise”. This will be the subject of Part II of this issue. The first part of this issue discusses the causes and effect of distortion. First, different types of distortion are described, followed by an explanation of how they are measured. This is followed by a discussion of the sources of distortion that may be present in hearing aids and the various mechanisms by which distortion is created. The final section of Part I discusses the effects of distortion on the hearing aid wearer. For the reader having difficulty understanding the technical concepts in the first part of this tutorial, a good overview from a different perspective has been presented by Kuk (1996). The second part of this issue discusses the causes and effects of internal noise in hearing aids. This part starts with a discussion of sources of internal noise and continues with a description of methods for the measurement of internal noise. This part concludes with a discussion of the perception of internal noise and its effects on the user of hearing aids. At the end of the text is an intentionally long list of references, which is intended to serve as a reasonably comprehensive resource for the reader seeking further information on distortion and noise in hearing aids.

Children who wear hearing aids may be at risk for further damage to their hearing from overamplification. Previous research on amplification-induced hearing loss has included children using linear amplification or simulations of predicted threshold shifts based on nonlinear amplification formulae. A relationship between threshold shifts and the use of nonlinear hearing aids in children has not been empirically verified. The purpose of the study was to compare predicted threshold shifts from amplification to longitudinal behavioral thresholds in a large group of children who wear hearing aids to determine the likelihood of amplification-induced hearing loss. An accelerated longitudinal design was used to collect behavioral threshold and amplification data prospectively. Two-hundred and thirteen children with mild-to-profound hearing loss who wore hearing aids were included in the analysis. Behavioral audiometric thresholds, hearing aid outputs, and hearing aid use data were collected for each participant across four study visits. Individual ear- and frequency-specific safety limits were derived based on the Modified Power Law to determine the level at which increased amplification could result in permanent threshold shifts. Behavioral thresholds were used to estimate which children would be above the safety limit at 500, 1000, 2000, and 4000 Hz using thresholds in dB HL and then in dB SPL in the ear canal. Changes in thresholds across visits were compared for children who were above and below the safety limits. Behavioral thresholds decreased across study visits for all children, regardless of whether their amplification was above the safety limits. The magnitude of threshold change across time corresponded with changes in ear canal acoustics as measured by the real-ear-to-coupler difference. Predictions of threshold changes due to amplification for children with hearing loss did not correspond with observed changes in threshold over across 2-4 yr of monitoring amplification. Use of dB HL thresholds and predictions of hearing aid output to set the safety limit resulted in a larger number of children being classified as above the safety limit than when safety limits were based on dB SPL thresholds and measured hearing aid output. Children above the safety limit for the dB SPL criteria tended to be fit above prescriptive targets. Additional research should seek to explain how the Modified Power Law predictions of threshold shift overestimated risk for children who wear hearing aids.

Some preliminary studies into the effectiveness of digital feedback correction schemes for open-ear hearing aids have been conducted. Three different hearing aids were used: (1) a commercially available behind-the-ear (BTE) hearing aid with an open earmold modified so that its internal filters and amplifiers were bypassed and the microphone and receiver connected directly to a digital signal processor, (2) the same BTE hearing aid with a closed earmold for comparison, and (3) a specially designed hearing aid with the microphone placed at the entrance to the ear canal and the receiver placed directly inside the ear canal. Off-line probing was used to determine the characteristics of the feedback path. In this experiment, the subjects had normal hearing. The addition of digital feedback control showed significant improvement in the available insertion gain from the open ear devices, as demonstrated in real ear measurements of the subjects.

Harvey Fletcher described the effect of a transmission channel on speech recognition in terms of the channel’s ‘‘articulation’’ plotted against channel gain. For normal listeners, articulation increases with gain to a maximum and then levels off or decreases. For hearing-impaired listeners, however, Fletcher noted: ‘‘... the gain αt corresponding to the tolerable level is reached before it is large enough (to bring articulation to a maximum).’’ This occurs in cochlear impairment because the dynamic range of hearing is reduced by recruitment. It is the problem to which the design of modern compression hearing aids is addressed. Compression aids compensate for recruitment by providing increased relative gain for weak speech sounds; thus they allow the articulation to reach higher values before tolerance levels are exceeded. An analysis of compression/equalization signal processing is presented. The essential elements of this processing are: (1) more than one channel of full-dynamic-range compression (the K-AMP design achieves similar results in a different way), (2) post-compression frequency-response shaping, and (3) adjustability of the compression in each channel, and of the equalization, to fit the amplified speech into the residual dynamic and frequency range of hearing of the individual patient.

Early hearing detection and communication development (EHDCD) programs enable us to identify hearing loss in early infancy, making intervention by 6 months of age a reasonable goal. For infants and children fitted with hearing instruments, it is critical that the devices be adjusted appropriately so that the pre-lingual listener has full and consistent access to sound, without discomfort for loud sounds. Several published pediatric amplification guidelines are available to assist clinicians with the hearing aid fitting process for infants and children.1-5 While the guidelines were developed in different jurisdictions, similar recommendations are made for all stages of the hearing instrument fitting process. For example, the use of a systematic, evidence-based approach to hearing aid fitting that accounts for an infant’s external ear acoustics at the assessment, selection, and verification stages and that includes the measurement of hearing aid output limiting is a requirement of every current pediatric amplification protocol. While it is encouraging to see consensus in pediatric hearing aid fitting guidelines, there continue to be substantial differences among clinical practice behaviors. Surveys have indicated that the majority of pediatric audiologists use sound field-aided threshold measures to verify the electroacoustic performance of hearing instruments for young infants.6 Probe-microphone measures were used by roughly 20% of the audiologists fitting hearing aids to infants.6 It has been well-documented that behavioral measures (i.e., aided threshold measures) do not provide accurate estimates of the aided audibility of soft, average, and loud speech or the real-ear saturation response of the hearing aid and that infants 6 months of age and younger are not developmentally capable of performing this task.7,8 Failure to appropriately verify the electroacoustic performance of the hearing aid in terms of predicted speech audibility and maximum hearing instrument output can result in obstructing the language benefits an infant would have otherwise received from being identified at an early age and optimally fitted. It is also important to consider the prescriptive targets used to determine the recommended levels for amplified speech and target limits for hearing instrument output as a function of frequency. Prescriptive algorithms provide the foundation on which the hearing instrument performance characteristics are selected for the infant or child to be fitted. Recent survey data indicate that most audiologists fitting hearing aids to infants and young children use a published hearing aid prescriptive procedure.6,9 At present, prescriptive procedures can be divided into two classifications: (1) evidence-based generic prescriptive algorithms and (2) manufacturer-specific proprietary algorithms. Evidence-based generic prescriptive algorithms for children include the DSL m[i/o]10 and the NAL-NL1,11 both of which are intended for use with any hearing aid. Proprietary prescriptive methods incorporate prescriptive algorithms developed by manufacturers for use with their specific hearing instruments. The lack of published information regarding the development of pediatric manufacturer-specific proprietary algorithms makes it difficult for the audiologist to make an informed choice about which procedure will be best for their young patient.12 Some manufacturers have decided to forego the development of a proprietary pediatric algorithm and use either the NAL or DSL prescriptive algorithms for fitting children and have implemented these formulas in their fitting software. These generic prescriptive algorithms may have been adapted by the manufacturer to account for the unique characteristics (e.g., compression kneepoint) of their hearing aids. Several investigators have compared proprietary prescriptive algorithms for use with adults. Keidser and colleagues found a 10-dB variation in the amount of gain prescribed by NAL-NL1, DSL[i/o], and four proprietary algorithms for the same audiogram.12 A study by Hawkins and Cook compared simulated 2-cc versus actual 2-cc gain as well as simulated insertion versus actual insertion gain measures from the fitting software for 28 hearing aids of various styles from four major manufacturers.13 Results indicated a clear trend for the simulated values to overestimate what was actually provided by the hearing aids for both the 2-cc coupler and insertion gain comparisons.13 Differences of as much as 10 to 20 dB were noted for the various hearing aids and prescriptive algorithms in the study. “...an infant can end up with

A careful hearing aid fitting requires consideration of various characteristics of inner ear pathology. The recruitment phenomenon restricts the dynamic range of the impaired hearing and this increase the demands on the hearing aids for a satisfactory correction of the frequency characteristics as well as for an intensity reduction at higher sound pressure level SPL. For years data from coupler or KEMAR (Knowles Electronics Manikin of Acoustical Research) have served to estimate the real ear gain of a hearing aid at higher input levels. In previous papers we reported on some of the differences between coupler measurement and probe tube measurement. The object of this study was to investigate the differences between these two methods at higher input SPL. Therefore, we measured the real ear insertion gain as well as the output characteristics with a 2 cm3 coupler in 80 patients at input levels of 60 dB, 80 dB and 100 dB. The results show differences between the two methods up to 30 dB in both directions in the single patient. Furthermore, the highest compression rate was found in the middle and high frequency range which are crucial for speech discrimination. Consequently, probe tube measurement should be used not only to adjust the frequency characteristics of the hearing aid but also to characterise the real effect of Automatic Gain Control AGC and Peak Clipping PC on insertion gain at higher input SPL. Multichannel hearing aids should be used whenever possible to reduce the disturbances to speech discrimination at low frequencies.

Three hearing aid manufacturers provided custom full-shell in-the-ear hearing aids for each of 3 hearing-impaired subjects. Each manufacturer was instructed that the hearing aids should provide the maximum possible acoustic gain within the limits of hearing aid shell size and available components. Coupler gain, insertion gain, and functional gain were measured for each hearing aid. Gain measures were made with the volume control at either the full-on setting or the highest setting possible before the onset of acoustical feedback. Full-on coupler gain curves were similar across all nine hearing aids. Individual differences in concha/ear canal size and in the fit of the hearing aids produced substantial variance in insertion gain across hearing aids. Peak insertion gain varied from 41 to 58 dB. If 10 dB reserve gain is allowed, the range of estimated peak use gain from these maximum-gain in-the-ear hearing aids is 31-48 dB.

Figure 2: Verbotonal training allows a child to hear her own voice using a microphone and headphones and to feel speech through the soundboard on her wrist.Neuroplasticity allows patients' brains to restructure themselves when the optimal frequency response (OFR) with hearing devices and regular auditory therapy are provided. But are we doing enough to facilitate this restructuring? Verbotonal rehabilitation, an auditory-based strategy that maximizes listening skills of those with hearing impairment and other communications disorders, simultaneously allows the development of intelligible spoken language through binaural listening. The verbotonal system includes diagnostic therapy, habilitation, rehabilitation, speech disorders, and foreign languages. First introduced in 1967 at the University of Tennessee, Knoxville, the method quickly expanded worldwide due to positive clinical outcomes, but clinicians still may not be taking advantage of some tools to improve word understanding for patients using hearing aids and cochlear implants. THE VIBROTACTILE PHASE What's the difference between the infant, child, and adult brain? Under age 5, a child can learn to speak two languages fluently. After puberty, a teenager has an adult brain, and it's difficult for him to learn a second language. Vibrotactile learning is optimal below age 2, which is why it is best to place hearing aids and cochlear implants in children under 5. Hearing specialists must adapt their strategy to infant, child, and adult brains. All infants learn from vibrotactile and proprioceptive input; the fetus feels and hears his mother's body and speech rhythms. After birth, the infant first feels and then hears through wide bandwidths of 2 Hz to 20,000 Hz. Verbotonal always begins with this wideband amplification regardless of the patient's age. At birth, vibrotactile and proprioceptive senses are more dominant than auditory senses, which strengthen as the child's brain develops. Verbotonal rehabilitation takes advantage of the early dominant vibrotactile sense with body movements to develop sound awareness using a VTU speech vibrator with a common bone vibrator. (Figure 1.) The vibrator responds from 2 Hz to 1000 Hz, and is attached to the infant's wrist or to a speech board. Using a speech vibrator, speech board, and headphone during therapy, a child can feel and hear his parent's voice and via a special microphone, a child can hear his own voice. (Figure 2.)Figure 1: Verbotonal rehabilitation takes advantage of the early dominant vibrotactile sense with body movements to develop sound awareness using a VTU speech vibrator with a common bone vibrator.Early vibrotactile input will establish sound awareness, and prepare the child's brain to accept speech through hearing aids, cochlear implants, or both. Most infants go through a preimplant evaluation stage where hearing aids are fitted bilaterally. With effective training, some infants can continue with hearing aids while others will need binaural cochlear implants as soon as possible. Developing a successful training program, however, takes careful planning. SPEECH, RHYTHM, INTONATION Hearing aids and cochlear implants should be adjusted to include low speech frequencies so the patient can hear the octave changes when a speaker's words have an emotional pitch. Changing vocal pitch adds meaning to speech, and is essential to word understanding. Verbotonal therapy sets hearing aids and cochlear implants to include speech frequencies below 300 Hz with a speech vibrator. A cochlear implant electrode at 188 Hz or lower is set to stimulate the client's neural reserve in the cochlea. Seven perceptual parameters are used for error analysis and correction. (Table 1.) Begin with speech modifications and move on to body movements. These corrections may be difficult at first, but because the hearing specialist has normal speech patterns, he can effectively correct errors. Infants and children may have balance and coordination problems so vestibular function should be assessed when possible. Reporting optimal octaves for each of the 40 phonemes is a helpful tool for analyzing perceptual errors, such as why a patient with a certain audiometric pattern makes a particular mistake. Optimal octaves also provide a foundation for the tonality perceptual continuum.Table 1: Body movements and speech modifications based on the parameters.OPTIMAL FREQUENCY RESPONSE The optimal frequency response changes with brain maturation and the progress patients make with therapy. Some clients may always need the speech vibrator while others will progress with only auditory input. The verbotonal clinician uses the VLU by changing the center frequency, bandwidth, and slopes to 0, 6, 12, 18, 20, or 60 dB/octave. Once the client's brain is trained under the OFR with the verbotonal system, the OFR is shifted toward an optimal hearing aid setting. As Robert Martin, PhD, noted in his March Hearing Journal column, patients will often comment during training, “If I could only hear like this with my hearing aids.” (See FastLinks.) With digital hearing aids and cochlear implants, gain needs to be adjusted independently in each of the 10 to 15 frequency bands to create the optimal frequency response. The slope toward low frequencies is an important adjustment for the wide flat frequency and bimodal (discontinuous) responses on the VTU and the hearing aid response. In 1972, Guberina constructed eight nonsense syllables as logatomes: /bru-bru, mu-mu, bu-bu, vo-vo, la-la, ke-ke, shi-shi, and si-si/. Asp developed a shortened three logatome test —/mu-mu, la-la, si-si/ — to evaluate detection and perception through VTU, hearing aids, and cochlear implants. Most often it is used without amplification in distance evaluation. Can the client repeat si-si correctly without using amplification or visual cues? If not, he has a high-frequency hearing loss. This is an effective screening tool for the tonality perceptual continuum. TONALITY PERCEPTUAL CONTINUUM The tonality perceptual continuum (TPC) is based on filtered optimal-octaves and the spectral pitch (tonality) of each phoneme. The TPC ranges from low to mid to high tonality. Verbotonal uses a phoneme, logatome, and word or sentence that is homogenous in tonality. For instance, /i/, /si-si/, cease, and “she is my sister” are all homogenous and in high tonality. At the low end of the tonality continuum are /u/, /mu-mu/, moon, and “mama blew a bubble.” Remember, the tonality continuum represents the frequencies on the cochlear continuum. If an error occurs in a lower tonality than the target tonality, change the optimum frequency response by adding high frequencies, reducing low frequencies, or both. Use the continuum for correcting errors. Phoneme and logatome testing are preferred because they minimize client guessing. The phoneme /i/ minimizes guessing but a word or a sentence includes guessing. Because the word level is important, we've included a list of homogenous tonality words in five categories: low, low-mid, mid, mid-high, and high. (Table 2.) These test words can be presented inside or outside the sound booth. Note that adding more gain in the high-frequency region may not always be the solution when a patient makes an error. With digital technology, the OFR can be used by altering the gain in individual frequency bands until good results are obtained. The prescribed frequency response is a starting point; the client's preference is key.Table 2: Homogenous tonality words.Conversational speaker-to-listener distance is three feet; the speech level is 65 dB SPL (50 dB HL) at the listener's ear. At two inches, the speech level is 95 dB SPL (80 dB HL). Use this as a reference. The hearing specialist must keep his normal speaking loudness at different distances to be effective. This takes discipline and training. Outside the booth, doubling the distance between the clinician and the client's ear reduces the speech signal by 6 dB; half the distance increases it 6 dB. With a tape line on the floor, increase the distance gradually until the client misses a word, then decrease the distance until the client correctly repeats it. This will help the client manage louder or softer speech and distances. Closer distances increase loudness and reduce the effect of noise and reverberation. MAKING UP FOR LOST TIME Placing hearing aids or cochlear implants at age 1 means the infant missed a whole year not hearing. How do we make up for lost time? Will he always be behind? Verbotonal uses intensive vibrotactile, proprioceptive, and body movement training to treat the infant because he needs to hear and feel speech all the time. Some hearing specialists use aided pure-tone thresholds within 20 dB HL to indicate normal hearing, but it's not that simple. Current thinking holds that normal cochlear implant thresholds mean normal hearing. That is, once the implant is programmed, the client will hear like normal hearing people. If this were true, the hearing specialist's job would be easy. Ironically, cochlear implants have created a need for effective habilitation or rehabilitation. Diagnostic therapy involves evaluation for implant candidacy, examination of speech recognition through hearing aids, preimplant counseling, initial programming of the implants, counseling, and the client repeating words, sentences, and paragraphs. As an option, verbotonal treatment includes perceptual parameters, tonality error analysis, and correction with a speech vibrator to feel and hear speech. OVERCOMING OBSTACLES Implementing verbotonal therapy is not without financial obstacles. Medicare and private insurers offer low reimbursement for aural rehabilitation and cochlear implant programming. Habilitation and rehabilitation therapy should already be included in the initial or follow-up hearing aid or cochlear implant visit. While using the verbotonal system will add 30 to 40 minutes to the visit, the patient will be satisfied with the new optimum frequency response, and will refer others to your clinic. The initial financial setback will provide an opportunity for increased earnings if the practitioner improves his client's word understanding. Remember, the best form of advertisement is good hearing aid or cochlear implant results. The Hearing Journal article, “Retraining the brain when hearing aids aren't enough,” noted that digital hearing aid technology has advanced, but the technology itself has not been able to resolve all the communication problems of the hearing impaired. (See FastLinks.) Whether the hearing specialist uses advanced hearing aid technology or cochlear implants, these devices are only a remediation tool for the defective peripheral hearing organ to send information to the brain. Unless we as hearing health care providers modify our thinking to change the way we practice, we are not doing enough to serve our clients. FastLinks • Read Dr. Robert Martin's Nuts and Bolts column on word understanding at http://bit.ly/WordUnderstanding. • Read “Retraining the brain when hearing aids aren't enough” at http://bit.ly/HJRetraining. • Comment about this article by writing to [email protected]. • Follow us on Twitter at twitter.com/hearingjournal.

Purpose: This study investigates the social support in both elderly who wear hearing aids and elderly who do not report any hearing loss.Methods: The study subjects were 48 seniors age 65 or older who wore hearing aids and 48 seniors who did not wear hearing aids. A Lubben social network scales survey was conducted. The Korean Version of International Outcome Inventory for Hearing Aids, Puretone Audiometry, and Word Recognition Score tests were carried out on the elderly who were wearing hearing aids.Results: A statistical analysis represented that the total social support scores were not significantly different between the two groups. Of all the social support factors, social network was statistically significant between the groups (p < 0.05), but social support was not statistically significant. The correlation between social support and the degree of hearing loss was not statistically significant. Further, there were no significant relationships found for the social support of older adults’ wearing hearing aids and satisfaction with hearing overall, and the level of social support.Conclusion: The results of the study indicated that users hearing aid users have a smaller social network than those who do not wear hearing aids. However, this result can be interpreted as an independent factor regarding satisfaction with hearing aid use and the degree of hearing. As a follow-up study, it will be necessary to proceed to study the diversity of the background factors for those elderly who do have hearing loss.

To investigate music appreciation in hearing aid (HA) users with varying levels of hearing loss (HL). Cross-sectional, within-subjects design. Tertiary medical center, community. Adults (≥18 yr) bilateral HA users. HA usage. Outcome variables included self-reported music enjoyment measures (pleasantness, musicality, naturalness) with and without HAs assessed with visual analogue scales (10 indicates highest level of enjoyment, 0 the least). Exposure variables include HL (better ear pure-tone average) and speech discrimination (word recognition scores [WRS]). Demographic information was collected. One hundred nine bilateral HA users completed the study. Mean (standard deviation) age was 66.6 years (16.8 yr); 52.3% were female patients. Mean (standard deviation) better ear pure-tone average was 51.1 dB (16.3 dB) HL. Increased severity of HL and worse WRS were associated with decreased music enjoyment ( p < 0.05) across all measures without HAs, adjusting for sex, age, education, race, HA type, age of HL diagnosis, duration of HL, duration of HA use, musical preference, and musical experience. However, these associations were attenuated or no longer significant with HA usage. Moreover, among all subjects, HAs (vs. no HAs) provided increased music enjoyment in pleasantness (HA, 6.94, no HA, 5.74; p < 0.01), musicality (HA, 7.35; no HA, 6.13, p < 0.01), and naturalness (HA, 6.75; no HA, 6.02; p = 0.02). HA users report increased music enjoyment with HAs compared with without HAs. Increased severity of HL and worse WRS were independently associated with decreased unaided music enjoyment. HA usage seems to mitigate this effect, particularly for those with worse HL.

Acclimatization in first-time hearing aid users using three different fitting protocols

A hearing aid is set forth that includes one or more hearing aid components that introduce an undesired undamped peak into the frequency response of the hearing aid. An electronic damping filter is utilized to compensate for the undamped peak. The electronic damping filter has a notch filter response that includes an inverse peak across the frequency range of the undamped peak thereby electronically damping the frequency response so that the hearing aid output is generally unaffected by the undesired characteristics of the inverse peak. The electronic damping filter may be programmable to vary the magnitude and/or shift the frequency of the inverse peak. A method is set forth that exploits this programmability and allows the same circuit topology to be used in two different hearing aids respectively having two different undamped peaks. A further method allows handling two or more peaks.

The goal of this study is to quantify a given hearing aid insertion gain using a consonant recognition based measure, for ears having sensorineural hearing loss. The basic question addressed is how a treatment impacts phone recognition, relative to a normal-hearing insertion gain. These tests are directed at (1) fine-tuning a treatment, with the ultimate goal of improving speech perception, and (2) to identify when a hearing level based treatment degrades speech recognition. Eight subjects with hearing loss were tested under two conditions: Flat-gain and a Treatment insertion gain based on subject's hearing level. The speech corpus consisted of consonant-vowel tokens at different signal to speech-weighted noise (SNR) conditions, presented at subjects’ most comfortable level. The tokens used in this study were selected from those having less than 3% error at -2 [dB] SNR, from 30 Normal Hearing subjects. The Treatment caused token score to improve for 31% of the trials and decrease for 12%. An analysis method was devised to identify degraded tokens for individual hearing impaired ears, based on sorting the tokens according to their error. By comparing sorted errors across experiments, the effect of the treatment could be accurately evaluated, providing precise characterization of idiosyncratic phone recognition.

Hearing aids have fundamental disadvantages: (1) stigmatization of the patient; (2) the sound is often found to be unsatisfactory due to the limited frequency range and undesired distortion; (3) in many patients, the ear canal fitting device generally necessary leads to an occlusion effect; (4) acoustic feedback when amplification is high. Conventional hearing aids transmit sound into the ear canal via a small microphone. Sound has the disadvantage of requiring high output sound pressure levels for its transmission. This along with the necessary miniaturization of the loudspeaker as well as the resonances and reflections in the closed ear canal contribute to the disadvantages mentioned. In contrast, implantable hearing aids do not make sound signals but micromechanical vibrations. An implantable hearing aid has an electromechanical transducer instead of the loudspeaker of a conventional hearing aid. The hearing signal does not leave the transducer as sound but as a mechanical vibration which is directly coupled to the auditory system bypassing the air. This implantable hearing aid is either coupled to the tympanic membrane, the ossicular chain, the perilymph of the inner ear, or the skull. An implantable hearing aid is expected to have: 1 Better sound fidelity than a hearing aid 2 No ear canal fitting device, free ear canal 3 No feedback 4 Invisibility Requirements on electronic hearing implants designed for patients with conductive hearing loss differ from those on implants for sensorineural hearing loss. Conductive hearing loss requires the implant to replace the impedance transformation, thus being an impedance transformation implant (ITI). In various respects, the demands on an ITI are lower than the demands on an electronic hearing aid for patients with sensorineural hearing loss. The latter are mostly patients with a failure of the cochlea amplifier (CA). A damage to the CA is clinically discernible by a positive recruitment and loss of otoacoustic emissions (OAE). Since these patients form the majority of cases with sensorineural hearing loss, an active hearing implant for such patients should partially replace the function of the CA. Therefore, the suggestion is to refer to a CAI (cochlea amplifier implant). The implant expressions ITI (for patients with conductive hearing loss) and CAI (for patients with sensorineural hearing loss) used in this context allow nomenclatural association with the CI (cochlear implant) for complete inner ear failure as well as with the BSI (brainstem implant) in the case of hearing nerve failure.

This study attempts to prescribe hearing aid characteristics for one listening environment selected by an individual hearing aid user in order to provide better speech intelligibility than standard insertion gain prescriptions. The procedure is based on acoustic analyses of noise recorded by the user. The main purpose is to show the feasibility of the measurement and analysis procedure as a tool to investigate the consequences of the noise characteristics of everyday hearing aid use. The Speech Intelligibility Index (SII) is used as a criterion to optimize the insertion gain frequency response of the hearing aid. The results indicate that realistic background noise information is essential to achieve the best possible speech audibility. Maximizing the SII required higher insertion gain above 5000 Hz than assumed in conventional fitting procedures. Different insertion gain frequency responses are required for different listening conditions. The measurement procedure could identify acoustic listening conditions where hearing instruments would probably give no benefit.