Commercial Hearing Aids Research Articles

An Implantable Piezofilm Middle Ear Microphone: Performance in Human Cadaveric Temporal Bones.

One of the major reasons that totally implantable cochlear microphones are not readily available is the lack of good implantable microphones. An implantable microphone has the potential to provide a range of benefits over external microphones for cochlear implant users including the filtering ability of the outer ear, cosmetics, and usability in all situations. This paper presents results from experiments in human cadaveric ears of a piezofilm microphone concept under development as a possible component of a future implantable microphone system for use with cochlear implants. This microphone is referred to here as a drum microphone (DrumMic) that senses the robust and predictable motion of the umbo, the tip of the malleus. The performance was measured by five DrumMics inserted in four different human cadaveric temporal bones. Sensitivity, linearity, bandwidth, and equivalent input noise were measured during these experiments using a sound stimulus and measurement setup. The sensitivity of the DrumMics was found to be tightly clustered across different microphones and ears despite differences in umbo and middle ear anatomy. The DrumMics were shown to behave linearly across a large dynamic range (46dB SPL to 100dB SPL) across a wide bandwidth (100Hz to 8kHz). The equivalent input noise (over a bandwidth of 0.1-10kHz) of the DrumMic and amplifier referenced to the ear canal was measured to be about 54dB SPL in the temporal bone experiment and estimated to be 46dB SPL after accounting for the pressure gain of the outer ear. The results demonstrate that the DrumMic behaves robustly across ears and fabrication. The equivalent input noise performance (related to the lowest level of sound measurable) was shown to approach that of commercial hearing aid microphones. To advance this demonstration of the DrumMic concept to a future prototype implantable in humans, work on encapsulation, biocompatibility, and connectorization will be required.

The electroacoustic performance of digital noise reduction systems in commercial hearing aids with Malay speech-plus-noise test signals

One of the most frequent complaints of hearing-impaired individuals is difficulty understanding speech in noisy environments. In order to improve listening comforts in background noise, digital noise reduction (DNR) has been incorporated into the hearing aid. However, each hearing aid manufacturer has their own proprietary algorithm for their DNR. Therefore, this study aimed to evaluate the efficacy of the DNR system in commercial hearing aids using the Malay speech-in-noise test. Electroacoustic testing has been performed on six hearing aids that have similar technology but different brands using newly developed Malay speech-in-noise test signals in the condition of DNR on and off. The total root-mean-square (RMS) gain reduction for each HA was calculated. The results show that the type of noise, the signal-to-noise ratio (SNR) and the gender of the speaker have a significant effect on the amount of gain reduction shown by the DNR of the tested hearing aids (p<0.05). In conclusion, clinicians need to measure and understand methods to verify the functionality of DNR before fitting a patient's hearing aid to ensure its effectiveness in real life.

Visualization and analysis of multi-channel dynamic range compression in hearing aids

One main functionality of hearing aids is restoring audibility. This means that low sound pressure levels are amplified above the elevated hearing threshold, and higher sound pressure levels do not exceed the individual uncomfortable loudness level (UCL). To this end, hearing aids provide frequency-dependent dynamic range compression which is denoted as hearing aid channels (HACs) in the recently published standard IEC 60118-16. As an increasing number of HACs, among other features, is one main feature to differentiate between price or technology levels, IEC 60118-16 includes a measurement procedure to verify the number of HACs. In this work, we verify this test procedure with a research hearing aid (RHA), and evaluate six commercial hearing aids of three different manufacturers and two technology levels. These results demonstrate the possibilities and limitations of the new test procedure. Furthermore, we introduced an extension of this test procedure with a channel-specific compression setting to overcome limitations and to get a deeper insight into the functionality of HACs in hearing aids. These results show that many HACs of commercial devices are coupled to neighboring frequencies, and that different strategies are used across manufacturers to adapt the number of HACs for different technology levels.

Comparing outcomes with the cloud-based and portable versions of an open-source hearing aid

The open-source speech processing platform (OSP) is an open-source hearing aid (HA), developed to overcome proprietary restrictions of commercial HAs and pave the way for innovative HA technology through rigorous and reproducible research. This study evaluates portable and cloud-based platforms of the OSP that will enable a wide range of lab and field applications. The two platforms share common software applications for HA signal processing and objective outcome assessments (HO2). The cloud-based platform is hosted on a web server whereas the portable platform is accessed on a browser via a WiFi-enabled portable communication device. Listeners with mild to moderately severe hearing loss or normal hearing completed a word identification task (Modified Rhyme Test) in a 6-alternate forced choice paradigm using the HO2 app. Words were mixed with different levels of speech-shaped noise; presented via calibrated headphones or behind-the-ear receivers-in-the-canal for cloud-based and portable platforms, respectively. Signals were processed with individualized gain and compression ratios based on a clinically validated prescriptive formula. Results-to-date from four listeners show comparable range of word identification scores between platforms. The full dataset will also compare phoneme-level scores and response time measures generated from the HO2 app. Clinical research applications will be discussed. [Work supported by NIH-R44DC020406.]

Acoustic feedback control in hearing aids with frequency warping

Acoustic Feedback Control continues to be a challenging problem due to the emerging form factors in advanced hearing aids and hearables, especially for severe and profound losses. In order to mitigate the effects of feedback in hearing aids, we present a novel use of frequency warping called “Freping,” for manipulating signals in the frequency domain. Freping is a non-linear transformation which breaks the similarity between the input and acoustic feedback signals of a hearing aid to prevent feedback. In this work, we implemented Freping in realtime for feedback management, as well as novel techniques to preserve the naturalness of sound. Our prior work has shown that Freping improves Added Stable Gain (ASG) in the presence of feedback while maintaining the same Hearing Aid Speech Quality Index (HASQI). We present new results for feedback management with Freping by performing “on-ear” measurements on an acoustic KEMAR manikin using standard hearing aid verification systems. We conducted feedback tests to measure the ASG with various configurations of Freping for various hearing loss levels using the NAL-NL2 prescriptions on a realtime open-source speech processing system for hearing aids. We also compare Freping feedback performance with that of commercial hearing aids.

CCi-MOBILE: A Portable Real Time Speech Processing Platform for Cochlear Implant and Hearing Research.

Experimental hardware-research interfaces form a crucial role during developmental stages of any medical, signal-monitoring system as it allows researchers to test and optimize output results before perfecting the design for the actual FDA approved medical device and large-scale production. These testing platforms, intake raw signals through which performance of novel algorithms can be analyzed and modified to generate the desired data points for an optimized output, allowing the advancement of the medical device. With cochlear implants (CIs) and hearing aids (HAs) becoming a more common solution for varying degrees of hearing impairment, having modern signal processing strategies tested for such speech sensitive systems is a necessity. But the rigid design requirements of commercial CI and HA processors make it difficult to explore novel algorithms for research investigations and conducting longitudinal studies. This study presents the design, development, clinical evaluation, and applications of CCi-MOBILE, a computationally powerful signal processing testing platform built for researchers in the hearing-impaired field. The custom-made, portable research platform allows researchers to design and perform complex speech processing algorithm assessment offline and in real-time. It can be operated through user-friendly, open-source software and is compatible with implants manufactured by Cochlear Corporation. The FPGA design and hardware processing pipeline for CI stimulation is discussed followed by results from an acute study with implant users' speech intelligibility in quiet and noisy conditions. The results show a consistent level of performance compared with CI users' clinical processor, thus confirming the viability of the platform in chronic CI based studies.

A Bayesian Modeling Approach to Situated Design of Personalized Soundscaping Algorithms

Effective noise reduction and speech enhancement algorithms have great potential to enhance lives of hearing aid users by restoring speech intelligibility. An open problem in today’s commercial hearing aids is how to take into account users’ preferences, indicating which acoustic sources should be suppressed or enhanced, since they are not only user-specific but also depend on many situational factors. In this paper, we develop a fully probabilistic approach to “situated soundscaping”, which aims at enabling users to make on-the-spot (“situated”) decisions about the enhancement or suppression of individual acoustic sources. The approach rests on a compact generative probabilistic model for acoustic signals. In this framework, all signal processing tasks (source modeling, source separation and soundscaping) are framed as automatable probabilistic inference tasks. These tasks can be efficiently executed using message passing-based inference on factor graphs. Since all signal processing tasks are automatable, the approach supports fast future model design cycles in an effort to reach commercializable performance levels. The presented results show promising performance in terms of SNR, PESQ and STOI improvements in a situated setting.

Effectiveness of a programable body-worn digital hearing aid for older adults in a developing country: a randomized controlled trial with a cross-over design

BackgroundHearing aids are important assistive devices for hearing rehabilitation. However, the cost of commonly available commercial hearing aids is often higher than the average monthly income of individuals in some developing countries. Therefore, there is a great need to locally produce cheaper, but still effective, hearing aids. The Thai-produced P02 hearing aid was designed to meet this requirement.ObjectiveTo compare the effectiveness of the P02 hearing aid with two common commercially available digital hearing aids (Clip-II™ and Concerto Basic®).MethodsA prospective, randomized controlled trial with a cross-over design was conducted from October 2012 to September 2014 in a rural Thai community. There were 73 participants (mean age of 73.7 ± 7.3 years) included in this study with moderate to severe hearing loss who were assessed for hearing aid performance, including probe microphone real-ear measurement, functional gain, speech discrimination, and participant satisfaction with the overall quality of perceived sound and the design of the device.ResultsThere were no statistically significant differences in functional gain or speech discrimination among the three hearing aids evaluated (p-value > 0.05). Real-ear measurements of the three hearing aids met the target curve in 93% of the participants. The best real-ear measurement of the hearing aid following the target curve was significantly lower than that of Clip-II™ and Concerto Basic® (p-value < 0.05) at high frequency. However, participants rated the overall quality of sound higher for the P02 hearing aid than that of Clip-II™ but lower than that of Concerto Basic® (p-value > 0.05). Participants revealed that the P02 hearing aid provided the highest satisfaction ratings for design and user-friendliness with statistical significance (p-value < 0.05).ConclusionThe P02 hearing aid was an effective device for older Thai adults with hearing disabilities. Additionally, its modern design, simplicity of use, and ease of maintenance were attractive to this group of individuals. These benefits support the rehabilitation potential of this hearing aid model and its positive impact on the quality of life of older adults in developing countries.Trial registrationThis study was registered under Clinicaltrial.govNCT01902914. Date of registration: July 18, 2013.

Effects of Hearing Aid Noise Reduction on Early and Late Cortical Representations of Competing Talkers in Noise.

ObjectivesPrevious research using non-invasive (magnetoencephalography, MEG) and invasive (electrocorticography, ECoG) neural recordings has demonstrated the progressive and hierarchical representation and processing of complex multi-talker auditory scenes in the auditory cortex. Early responses (<85 ms) in primary-like areas appear to represent the individual talkers with almost equal fidelity and are independent of attention in normal-hearing (NH) listeners. However, late responses (>85 ms) in higher-order non-primary areas selectively represent the attended talker with significantly higher fidelity than unattended talkers in NH and hearing–impaired (HI) listeners. Motivated by these findings, the objective of this study was to investigate the effect of a noise reduction scheme (NR) in a commercial hearing aid (HA) on the representation of complex multi-talker auditory scenes in distinct hierarchical stages of the auditory cortex by using high-density electroencephalography (EEG).DesignWe addressed this issue by investigating early (<85 ms) and late (>85 ms) EEG responses recorded in 34 HI subjects fitted with HAs. The HA noise reduction (NR) was either on or off while the participants listened to a complex auditory scene. Participants were instructed to attend to one of two simultaneous talkers in the foreground while multi-talker babble noise played in the background (+3 dB SNR). After each trial, a two-choice question about the content of the attended speech was presented.ResultsUsing a stimulus reconstruction approach, our results suggest that the attention-related enhancement of neural representations of target and masker talkers located in the foreground, as well as suppression of the background noise in distinct hierarchical stages is significantly affected by the NR scheme. We found that the NR scheme contributed to the enhancement of the foreground and of the entire acoustic scene in the early responses, and that this enhancement was driven by better representation of the target speech. We found that the target talker in HI listeners was selectively represented in late responses. We found that use of the NR scheme resulted in enhanced representations of the target and masker speech in the foreground and a suppressed representation of the noise in the background in late responses. We found a significant effect of EEG time window on the strengths of the cortical representation of the target and masker.ConclusionTogether, our analyses of the early and late responses obtained from HI listeners support the existing view of hierarchical processing in the auditory cortex. Our findings demonstrate the benefits of a NR scheme on the representation of complex multi-talker auditory scenes in different areas of the auditory cortex in HI listeners.

Interactions Between Digital Noise Reduction and Reverberation: Acoustic and Behavioral Effects.

Digital noise reduction (DNR) processing is used in hearing aids to enhance perception in noise by classifying and suppressing the noise acoustics. However, the efficacy of DNR processing is not known under reverberant conditions where the speech-in-noise acoustics are further degraded by reverberation. The purpose of this study was to investigate acoustic and perceptual effects of DNR processing across a range of reverberant conditions for individuals with hearing impairment. This study used an experimental design to investigate the effects of varying reverberation on speech-in-noise processed with DNR. Twenty-six listeners with mild-to-moderate sensorineural hearing impairment participated in the study. Speech stimuli were combined with unmodulated broadband noise at several signal-to-noise ratios (SNRs). A range of reverberant conditions with realistic parameters were simulated, as well as an anechoic control condition without reverberation. Reverberant speech-in-noise signals were processed using a spectral subtraction DNR simulation. Signals were acoustically analyzed using a phase inversion technique to quantify improvement in SNR as a result of DNR processing. Sentence intelligibility and subjective ratings of listening effort, speech naturalness, and background noise comfort were examined with and without DNR processing across the conditions. Improvement in SNR was greatest in the anechoic control condition and decreased as the ratio of direct to reverberant energy decreased. There was no significant effect of DNR processing on speech intelligibility in the anechoic control condition, but there was a significant decrease in speech intelligibility with DNR processing in all of the reverberant conditions. Subjectively, listeners reported greater listening effort and lower speech naturalness with DNR processing in some of the reverberant conditions. Listeners reported higher background noise comfort with DNR processing only in the anechoic control condition. Results suggest that reverberation affects DNR processing using a spectral subtraction algorithm in such a way that decreases the ability of DNR to reduce noise without distorting the speech acoustics. Overall, DNR processing may be most beneficial in environments with little reverberation and that the use of DNR processing in highly reverberant environments may actually produce adverse perceptual effects. Further research is warranted using commercial hearing aids in realistic reverberant environments.

Noise management features of the open speech platform

In this contribution, we present the noise management features of the Open Speech Platform (OSP) for hearing aid (HA) research. OSP includes basic HA modules (i) subband decomposition, (ii) wide dynamic range compression and (iii) adaptive feedback cancellation; a baseline single-channel speech enhancement (SE) based on Wiener filtering for noise subtraction. We extended OSP noise management to include a generalized sidelobe cancellation (GSC) beamforming between left and right channels, followed by the SE. Time is the scarcest resource, followed by central processing unit (CPU) resources in commercial HAs. With the proposed GSC + SE approach, we were both time and CPU limited. Release 2019a of OSP has 5.6 ms end-to-end latency and GSC requires an additional 5 ms, putting us above the 10 ms requirement. The wearable device of OSP has 4 cores, C0 – C3. C0 is used for all non-realtime tasks such as kernel, embedded web server, etc. and remaining cores are used for realtime tasks. Naive realization of GSC results in one or more cores not meeting the realtime constraints, resulting in audible artifacts. We present optimizations to meet time and CPU budgets; and preliminary objective and subjective results of the proposed system.

Using Objective Metrics to Measure Hearing Aid Performance.

The performance of hearing aids is generally characterized by a small set of standardized measurements. The primary goals of these procedures are to measure basic aspects of the hearing aid performance and to ascertain that the device is operating properly. A more general need exists for objective metrics that can predict hearing aid outcomes. Such metrics must consider the interaction of all the signal processing operating in the hearing aid and must do so while also accounting for the hearing loss for which the hearing aid has been prescribed. This article represents a first step in determining the clinical applicability of the hearing aid speech perception index (HASPI) intelligibility and hearing aid speech quality index (HASQI) speech quality metrics. The goals of this article are to demonstrate the feasibility of applying these metrics to commercial hearing aids and to illustrate the anticipated range of measured values and identify implementation concerns that may not be present for conventional measurements. This article uses the HASPI intelligibility and HASQI speech quality metrics to measure the performance of commercial hearing aids. These metrics measure several aspects of the processed signal, including envelope fidelity, modifications of the temporal fine structure, and changes in the long-term frequency response, all in the context of an auditory model that reproduces the salient aspects of the peripheral hearing loss. The metrics are used to measure the performance of basic and premium hearing aids from three different manufacturers. Test conditions include the environmental factors of signal to noise ratio and presentation level, and the fitting configurations were varied to provide different degrees of processing from linear to aggressive nonlinear processing for two different audiograms. The results show that the metrics are capable of measuring statistically significant differences across devices and processing settings. HASPI and HASQI measure both audibility and nonlinear distortion in the devices, and conditions are identified where predicted intelligibility is high but predicted speech quality is substantially reduced. The external signal properties of signal to noise ratio and presentation level are both statistically significant. Hearing loss is significant for HASPI but not for HASQI, and degree of processing is significant for both metrics. A quadratic model for manufacturer showed large effect sizes for HASPI and HASQI, but basic versus premium hearing aid model is not significant. The results presented in this article represent a first step in applying the HASPI and HASQI metrics to commercial hearing aids. Modern hearing aids often use several different processing strategies operating simultaneously. The proposed metrics provide a way to predict the total effect of this processing, including algorithm interactions that may be missed by conventional measurement procedures. The measurements in this article show significant differences between manufacturers, processing settings, and adjustment for different hearing losses. No significant differences were found between basic and premium hearing aid models. Further research will be needed to determine the clinical relevance of these measurements and to provide target values appropriate for successful fittings.

Audiologic evaluation of the tympan open source hearing aid

The “Tympan” open source hearing aid (Creare LCC) was developed in response to needs identified by the 2014 Open Speech Signal Processing Platform Workshop hosted by NIH. The Tympan Phase I prototype is a neck-worn device with external microphones and headphones implemented on a Teensy 3.6 development board and Arduino software platform. Custom-designed electronics for audio input acquisition, digital signal processing, power management, and wireless communication allows expert users to create new algorithms directly in firmware. Operating in parallel, a custom software interface allows “occasional” users with the necessary support to modify easily parameters of existing algorithms. A variety of electroacoustic analyses, including throughput delay, amplitude compression input/output curves and time constants, harmonic distortion, internal noise, frequency response, and other real-ear measurements were performed on the Phase I prototype using commercial hearing aid analyzers and compared to today’s premium...

A Realtime, Open-Source Speech-Processing Platform for Research in Hearing Loss Compensation.

We are developing a realtime, wearable, open-source speech-processing platform (OSP) that can be configured at compile and run times by audiologists and hearing aid (HA) researchers to investigate advanced HA algorithms in lab and field studies. The goals of this contribution are to present the current system and propose areas for enhancements and extensions. We identify (i) basic and (ii) advanced features in commercial HAs and describe current signal processing libraries and reference designs to build a functional HA. We present performance of this system and compare with commercial HAs using "Specification of Hearing Aid Characteristics," the ANSI 3.22 standard. We then describe a wireless protocol stack for remote control of the HA parameters and uploading media and HA status for offline research. The proposed architecture enables advanced research to compensate for hearing loss by offloading processing from ear-level-assemblies, thereby eliminating the bottlenecks of CPU and communication between left and right HAs.

Tolerable delay for speech production and perception: effects of hearing ability and experience with hearing aids

Objective: Processing delay is one of the important factors that limit the development of novel algorithms for hearing devices. In this study, both normal-hearing listeners and listeners with hearing loss were tested for their tolerance of processing delay up to 50 ms using a real-time setup for own-voice and external-voice conditions based on linear processing to avoid confounding effects of time-dependent gain. Design: Participants rated their perceived subjective annoyance for each condition on a 7-point Likert scale. Study sample: Twenty normal-hearing participants and twenty participants with a range of mild to moderate hearing losses. Results: Delay tolerance was significantly greater for the participants with hearing loss in two out of three voice conditions. The average slopes of annoyance ratings were negatively correlated with the degree of hearing loss across participants. A small trend of higher tolerance of delay by experienced users of hearing aids in comparison to new users was not significant. Conclusion: The increased tolerance of processing delay for speech production and perception with hearing loss and reduced sensitivity to changes in delay with stronger hearing loss may be beneficial for novel algorithms for hearing devices but the setup used in this study differed from commercial hearing aids.

Directional Processing and Noise Reduction in Hearing Aids: Individual and Situational Influences on Preferred Setting.

A better understanding of individual differences in hearing aid (HA) outcome is a prerequisite for more personalized HA fittings. Currently, knowledge of how different user factors relate to response to directional processing (DIR) and noise reduction (NR) is sparse. To extend a recent study linking preference for DIR and NR to pure-tone average hearing thresholds (PTA) and cognitive factors by investigating if (1) equivalent links exist for different types of DIR and NR, (2) self-reported noise sensitivity and personality can account for additional variability in preferred DIR and NR settings, and (3) spatial target speech configuration interacts with individual DIR preference. Using a correlational study design, overall preference for different combinations of DIR and NR programmed into a commercial HA was assessed in a complex speech-in-noise situation and related to PTA, cognitive function, and different personality traits. Sixty experienced HA users aged 60-82 yr with controlled variation in PTA and working memory capacity took part in this study. All of them had participated in the earlier study, as part of which they were tested on a measure of "executive control" tapping into cognitive functions such as working memory, mental flexibility, and selective attention. Six HA settings based on unilateral (within-device) or bilateral (across-device) DIR combined with inactive, moderate, or strong single-microphone NR were programmed into a pair of behind-the-ear HAs together with individually prescribed amplification. Overall preference was assessed using a free-field simulation of a busy cafeteria situation with either a single frontal talker or two talkers at ±30° azimuth as the target speech. In addition, two questionnaires targeting noise sensitivity and the "Big Five" personality traits were administered. Data were analyzed using multiple regression analyses and repeated-measures analyses of variance with a focus on potential interactions between the HA settings and user factors. Consistent with the earlier study, preferred HA setting was related to PTA and executive control. However, effects were weaker this time. Noise sensitivity and personality did not interact with HA settings. As expected, spatial target speech configuration influenced preference, with bilateral and unilateral DIR "winning" in the single- and two-talker scenario, respectively. In general, participants with higher PTA tended to more strongly prefer bilateral DIR than participants with lower PTA. Although the current study lends some support to the view that PTA and cognitive factors affect preferred DIR and NR setting, it also indicates that these effects can vary across noise management technologies. To facilitate more personalized HA fittings, future research should investigate the source of this variability.

Fitting Frequency-Lowering Signal Processing Applying the American Academy of Audiology Pediatric Amplification Guideline: Updates and Protocols.

Although guidelines for fitting hearing aids for children are well developed and have strong basis in evidence, specific protocols for fitting and verifying technologies can supplement such guidelines. One such technology is frequency-lowering signal processing. Children require access to a broad bandwidth of speech to detect and use all phonemes including female /s/. When access through conventional amplification is not possible, the use of frequency-lowering signal processing may be considered as a means to overcome limitations. Fitting and verification protocols are needed to better define candidacy determination and options for assessing and fine tuning frequency-lowering signal processing for individuals. This work aims to (1) describe a set of calibrated phonemes that can be used to characterize the variation in different brands of frequency-lowering processors in hearing aids and the verification with these signals and (2) determine whether verification with these signal are predictive of perceptual changes associated with changes in the strength of frequency-lowering signal processing. Finally, we aimed to develop a fitting protocol for use in pediatric clinical practice. Study 1 used a sample of six hearing aids spanning four types of frequency lowering algorithms for an electroacoustic evaluation. Study 2 included 21 adults who had hearing loss (mean age 66 yr). Simulated fricatives were designed to mimic the level and frequency shape of female fricatives extracted from two sources of speech. These signals were used to verify the frequency-lowering effects of four distinct types of frequency-lowering signal processors available in commercial hearing aids, and verification measures were compared to extracted fricatives made in a reference system. In a second study, the simulated fricatives were used within a probe microphone measurement system to verify a wide range of frequency compression settings in a commercial hearing aid, and 27 adult listeners were tested at each setting. The relation between the hearing aid verification measures and the listener's ability to detect and discriminate between fricatives was examined. Verification measures made with the simulated fricatives agreed to within 4 dB, on average, and tended to mimic the frequency response shape of fricatives presented in a running speech context. Some processors showed a greater aided response level for fricatives in running speech than fricatives presented in isolation. Results with listeners indicated that verified settings that provided a positive sensation level of /s/ and that maximized the frequency difference between /s/ and /∫/ tended to have the best performance. Frequency-lowering signal processors have measureable effects on the high-frequency fricative content of speech, particularly female /s/. It is possible to measure these effects either with a simple strategy that presents an isolated simulated fricative and measures the aided frequency response or with a more complex system that extracts fricatives from running speech. For some processors, a more accurate result may be achieved with a running speech system. In listeners, the aided frequency location and sensation level of fricatives may be helpful in predicting whether a specific hearing aid fitting, with or without frequency-lowering, will support access to the fricatives of speech.

The Performance of Music and Speech with Different Frequency Lowering Devices

Objective: Previous research studies have documented the benefits of both frequency transposition (FT) and non-linear frequency compression (NLFC) for patients with different degrees of hearing loss, however, very few studies directly compare the effect of two different frequency lowering (FL) techniques on the same population to investigate if superior performance in terms of speech and music perception exists. Design and Sample: The aim of the study was to determine whether people with a moderate to severe hearing loss have improved music perception and speech intelligibility with the use of FL and if the benefits is dependent on a specific FL strategy. A parallel research design was implemented and a purposive sampling method was used. Participants (n=20) were experienced hearing aid users with bilateral, moderate to severe hearing losses and no FL experience. A music perception questionnaire were completed by participants to rate their perception of music and the Music Perception Test (MPT) were used to assess participants’ musical performance. The Phoneme Perception Test (PPT) and Hearing-in-Noise Test (HINT) were used to assess participants’ speech perception abilities. Two commercial hearing aid devices with different FL approaches (FT and NLFC) were used. Results and Conclusion: Results indicate that participants distinguish high frequency sounds better with both FL strategies than without it resulting in better speech intelligibility in quiet and in noise. Greater speech scores with NLFC compared to FT was evident. Participants that used FT showed more confusion regarding speech perception. In terms of music perception the study shows that NLFC improves participants’ pitch and melody perception whereas mostly no musical improvement was observed with FT. With the use of FT participants’ ability to identify melodies decreased. A strong preference to listen to classical music with NLFC compared to FT was noted. Therefore it is evident that FL can improve speech and music perception for people with moderate to severe hearing losses but the perceived benefit seems to be dependent on the specific FL strategy implemented.

A Cotton Wick Improves Hearing in a Patient with Profound Hearing Loss

Dear Editor,&#x0D; &#x0D; The tympanic membrane and the ossicular chain contribute roughly 28 dB in hearing gain. In chronic suppurative otitis media, loss of tympanic membrane and lysis of the ossicular chain are significant causes of hearing loss.1 Through the years, hearing impairment has been augmented using various devices such as ear trumpets, carbon hearing aids, vacuum tube and transistor hearing aids, bone anchored hearing aids, and cochlear implants.2 This case report describes how a cotton wick was used to amplify sound.&#x0D; &#x0D; Case Report&#x0D; A 65-year-old man consulted for hearing loss. He had a childhood history of recurrent ear discharge and hearing loss and was diagnosed with chronic suppurative otitis media. At age 55, he underwent tympanomastoidectomy of the left ear. While surgery stopped the left ear discharge, there was complete hearing loss in this ear. For this reason, he opted not to have surgery on the right ear. There was subsequent recurrent ear disease of the right ear. He would clean his ear with a cotton wick and apply antibiotic drops during bouts of ear discharge. He observed that leaving the ear wick with a few drops of topical otic preparations (polymyxin-neomycin-steroid or ofloxacin) would lessen the frequency of ear discharge and improve his hearing. He found that morning application and positioning of the cotton wick in his right ear using tweezers and a toothpick allowed him to hear adequately to conduct his daily activities as an architect. (Figure 1, 2) The fear of hearing loss from another surgery, cost of a commercial hearing aid, and great utility of a simple cotton wick made him continue his practice for these ten years.&#x0D; Examination of the right middle ear without the cotton wick showed thickened mucosa, absent malleus and incus structures, a patent Eustachian tube and a near – total tympanic membrane perforation. There was no keratinous material or foul smelling discharge. (Figure 3) Pure tone audiometry confirmed that with the cotton wick, the right air-bone gap decreased at 500 hz, 1kHz, 2Kh and 4KHz by 30db, 40dB, 35dB and 25dB respectively. (Table 1)&#x0D; DISCUSSION&#x0D; At different anatomic levels, mechanical sound energy is amplified and transmitted to the functional parts of the ear. The tympanic membrane and oval window ratio of 21:1 and malleus-incus lever mechanism ratio of 1.3:1 provide a 28 dB amplification of conductive hearing.1 This gain is reflected by frequency specific air-bone gaps, which can range between 25-40 dB. With the contribution from the external ear, the overall conductive gain is 60 dB.1,3 Damage to the auditory system often results in a loss of hearing sensitivity that is frequency – specific. The presence of a frequency – specific wide air-bone gap suggests ossicular chain discontinuity among patients with chronic otitis media.4 Narrowing of the air-bone gap, which in this case was provided by insertion of the cotton wick, may lead to at least partial restoration of ossicular coupling.&#x0D; The ability of the cotton wick to improve hearing may be attributed to its possession of characteristics for sound conduction and acoustic impedance, such as stiffness, resistance and mass. The effectiveness of the cotton wick was reported to be dependent on its positioning in the ear; the patient would have to insert the wick down to the level of the promontory or oval window, occasionally blow his nose, or reposition the cotton wick to achieve an acceptable hearing level. However, for a patient with completely deaf contralateral ear, a 32.5 dB gain in hearing is very pronounced and significant. &#x0D; The hearing gain produced by the cotton wick only amplified the air conductive component of hearing but not bone conduction. While it afforded amplification of sound and a route of medicine administration, it may also have contributed to sensorineural hearing loss brought about by ototoxicity of medications and thickening of the oval and round window from chronic irritation. For this reason, utmost caution must be advised before considering use of a “cotton wick” to amplify hearing in this manner-- a practice we do not endorse.&#x0D; The cotton wick may have served as a vibrating piston on top of the oval window which amplified hearing. Such a mechanism may conceivably prognosticate potential gain from a contemplated tympanoplasty in the same way that the “paper patch test”5 predicts simple myringoplasty outcomes. Having said that, the diagnostic utility of such a cotton wick requires further investigation before potential clinical applications such as prognostication of tympanoplasty are theorized. Could future studies show that a preoperative cotton wick (or equivalent device) may approximate potential gains from a good tympanoplasty with ossiculoplasty in a patient with total tympanic perforation and ossicular chain loss?&#x0D; &#x0D; Sincerely,&#x0D; Ryner Jose D. Carrillo, MD, MSc&#x0D; Precious Eunice R. Grullo, MD, MPH&#x0D; Maria Luz M. San Agustin, RN, MClinAudio&#x0D; &#x0D;

Comparing NAL-NL1 and DSL v5 in Hearing Aids Fit to Children with Severe or Profound Hearing Loss: Goodness of Fit-to-Targets, Impacts on Predicted Loudness and Speech Intelligibility.

An important goal of providing amplification to children with hearing loss is to ensure that hearing aids are adjusted to match targets of prescriptive procedures as closely as possible. The Desired Sensation Level (DSL) v5 and the National Acoustic Laboratories' prescription for nonlinear hearing aids, version 1 (NAL-NL1) procedures are widely used in fitting hearing aids to children. Little is known about hearing aid fitting outcomes for children with severe or profound hearing loss. The purpose of this study was to investigate the prescribed and measured gain of hearing aids fit according to the NAL-NL1 and the DSL v5 procedure for children with moderately severe to profound hearing loss; and to examine the impact of choice of prescription on predicted speech intelligibility and loudness. Participants were fit with Phonak Naida V SP hearing aids according to the NAL-NL1 and DSL v5 procedures. The Speech Intelligibility Index (SII) and estimated loudness were calculated using published models. The sample consisted of 16 children (30 ears) aged between 7 and 17 yr old. The measured hearing aid gains were compared with the prescribed gains at 50 (low), 65 (medium), and 80 dB SPL (high) input levels. The goodness of fit-to-targets was quantified by calculating the average root-mean-square (RMS) error of the measured gain compared with prescriptive gain targets for 0.5, 1, 2, and 4 kHz. The significance of difference between prescriptions for hearing aid gains, SII, and loudness was examined by performing analyses of variance. Correlation analyses were used to examine the relationship between measures. The DSL v5 prescribed significantly higher overall gain than the NAL-NL1 procedure for the same audiograms. For low and medium input levels, the hearing aids of all children fit with NAL-NL1 were within 5 dB RMS of prescribed targets, but 33% (10 ears) deviated from the DSL v5 targets by more than 5 dB RMS on average. For high input level, the hearing aid fittings of 60% and 43% of ears deviated by more than 5 dB RMS from targets of NAL-NL1 and DSL v5, respectively. Greater deviations from targets were associated with more severe hearing loss. On average, the SII was higher for DSL v5 than for NAL-NL1 at low input level. No significant difference in SII was found between prescriptions at medium or high input level, despite greater loudness for DSL v5 than for NAL-NL1. Although targets between 0.25 and 2 kHz were well matched for both prescriptions in commercial hearing aids, gain targets at 4 kHz were matched for NAL-NL1 only. Although the two prescriptions differ markedly in estimated loudness, they resulted in comparable predicted speech intelligibility for medium and high input levels.