Cochlear Implants Sound Processors Research Articles

Long-Term Cochlear Implant Sound Processor Usage in Children with Single-Sided Deafness.

To assess cochlear implant (CI) sound processor usage over time in children with single-sided deafness (SSD) and identify factors influencing device use. Retrospective, chart review study. Pediatric tertiary referral center. Children with SSD who received CI between 2014 and 2020. Primary outcome was average daily CI sound processor usage over follow-up. Fifteen children with SSD who underwent CI surgery were categorized based on age of diagnosis and surgery timing. Over an average of 4.3-year follow-up, patients averaged 4.6 hours/day of CI usage. Declining usage trends were noted over time, with the first 2 years postactivation showing higher rates. No significant usage differences emerged based on age, surgery timing, or hearing loss etiology. Long-term usage decline necessitates further research into barriers and enablers for continued CI use in pediatric SSD cases.

Understanding Patient Utilization Patterns of Cochlear Implant Processors.

To evaluate the extent of benefit the second processor provides and to better understand utilization patterns regarding cochlear implant (CI) sound processors. Institutional contracts determine the external CI sound processor hardware that a patient is eligible for. Despite the high prevalence of CI worldwide, there is a paucity in the literature regarding patient preferences and how patients utilize provided external hardware. A close-ended, multiple-choice survey was mailed to all patients over the age of 18 years who underwent CI between 2016 to 2020 at a tertiary academic medical center. Patients who received their CI hardware prior to 2018 were provided 2 processors, whereas those who received their hardware in 2018 or later were provided 1 processor. A total of 100/263 surveys were returned for a response rate of 38.0%. Of the cohort with 1 processor, 31.3% experienced a period without a functioning processor and access to sound compared to 5.6% of the cohort with 2 processors (P = -.003). Of the cohort with 2 processors, 24.3% noted that they often or always utilize their second processor. When asked how important having a second processor was, 62.9% of the 2-processor group responded that it was very important (P = .001). The most common reason for utilizing the second processor was a damaged primary processor. Patients who received 2 processors had a significantly lower number of postoperative audiology clinic visits for device troubleshooting (P < .001). Patients who have 2 CI external processors identify this as being very important to them and experience significantly less time without access to sound due to lack of a functioning processor. As institutional contracts often dictate whether a patient will receive 1 or 2 sound processors with their CI hardware, it is important to understand patient preferences and utilization patterns in order to guide patient-centric policies.

Speech Understanding and Subjective Listening Effort in Noise With Different OTEs and Sound Processing Technologies.

To determine speech reception thresholds (SRTs) in noise and subjective listening effort (LE) in cochlear implant (CI) recipients for application of three sound processing (SP) technologies with two off-the-ear (OTE) CI sound processors, a fixed moderately directional microphone (Standard), an adaptive directional microphone (Beam), and the spatial noise-reduction setting ForwardFocus, with the Kanso 2 (OTE2), and Beam with the Kanso (OTE1). Prospective repeated measures, within-subject design. Single tertiary-referral center. Twenty CI recipients with bilateral severe-to-profound sensorineural hearing loss. SRTs were assessed in two spatial configurations with frontal speech and noise from 90-180-270 degrees (S0N90-180-270) or from the CI side (S0NCI). SRTs were obtained for sentences of the Oldenburg sentence test presented in International Collegium of Rehabilitative Audiology (ICRA) noise ICRA5-250. LE for speech understanding in noise was evaluated in S0N90-180-270 and assessed in effort scale categorical units (ESCUs) by using Adaptive Categorical Listening Effort Scaling (ACALES). LEs at 5-dB signal-to-noise ratio (SNR) were calculated from fitted psychometric curves. With OTE2 in S0N90-180-270, SRT with ForwardFocus (-4.28 dB SNR) was better than with Beam (-3.13 dB SNR) and Standard (0.43 dB SNR). ForwardFocus showed lower LE5dB (2.61 ESCU) compared with Beam (4.60 ESCU) and Standard (5.32 ESCU). In a comparison of both OTEs in S0N90-180-270 regarding best-performing SP technology, ForwardFocus with OTE2 yielded a better SRT and better LE5dB than Beam with OTE1 (SRT: -1.70 dB SNR; LE5dB: 4.00 ESCU). With OTE2 in S0NCI, SRT was improved with ForwardFocus (-2.78 dB SNR) compared with Beam (-1.23 dB SNR) and Standard (1.83 dB SNR). With respect to SP technology and OTE, CI recipients experience best SRT and lowest LE in S0N90-180-270 when using ForwardFocus with OTE2. ACALES is feasible for assessing subjective LE in CI recipients.

Comparison of an Implantable Middle Ear Microphone and Conventional External Microphone for Cochlear Implants: A Clinical Feasibility Study.

All commercially available cochlear implant (CI) systems use an external microphone and sound processor; however, external equipment carries lifestyle limitations. Although totally implantable devices using subcutaneous microphones have been developed, these are compromised by problems with soft tissue sound attenuation, feedback, and intrusive body noise. This in vivo pilot study evaluates a middle ear microphone (MEM) that aims to overcome these issues and compares hearing performance with that of an external CI microphone. Six adult participants with an existing CI were implanted with a temporary MEM in the contralateral ear. Signals from the MEM were routed via a percutaneous plug and cable to the CI sound processor. Testing was performed in the CI microphone and MEM conditions using a range of audiometric assessments, which were repeated across four visits. Performance of the MEM did not differ significantly from that of the CI on the assessments of Auditory Speech Sounds Evaluation loudness scaling at either 250 or 1000 Hz, or in the accuracy of repeating keywords presented at 70 dB. However, the MEM had significantly poorer aided sound-field thresholds, particularly at higher frequencies (≥4000 Hz), and significantly poorer performance on Arthur Boothroyd words presented at 55 dB, compared with the CI. In this pilot study, the MEM showed comparable performance to that of an external CI microphone across some audiometric assessments. However, performance with the MEM was poorer than the CI in soft-level speech (55 dB) and at higher frequencies. As such, the benefits of MEM need to be considered against the compromises in hearing performance. However, with future development, MEM is a potentially promising technology.

Remote Microphone Systems for Cochlear Implant Recipients in Small Group Settings.

Cochlear implant (CI) recipients often experience speech recognition difficulty in noise in small group settings with multiple talkers. In traditional remote microphones systems, one talker wears a remote microphone that wirelessly delivers speech to the CI processor. This system will not transmit signals from multiple talkers in a small group. However, remote microphone systems with multiple microphones allowing for adaptive beamforming may be beneficial for small group situations with multiple talkers. Specifically, a remote microphone with an adaptive multiple-microphone beamformer may be placed in the center of the small group, and the beam (i.e., polar lobe) may be automatically steered toward the direction associated with the most favorable speech-to-noise ratio. The signal from the remote microphone can then be wirelessly delivered to the CI sound processor. Alternately, each of the talkers in a small group may use a remote microphone that is part of a multi-talker network that wirelessly delivers the remote microphone signal to the CI sound processor. The purpose of this study was to compare the potential benefit of an adaptive multiple-microphone beamformer remote microphone system and a multi-talker network remote microphone system. Twenty recipients, ages 12 to 84 years, with Advanced Bionics CIs completed sentence-recognition-in-noise tasks while seated at a desk surrounded by three loudspeakers at 0, 90, and 270 degrees. These speakers randomly presented the target speech while competing noise was presented from four loudspeakers located in the corners of the room. Testing was completed in three conditions: 1) CI alone, 2) Remote microphone system with an adaptive multiple-microphone beamformer, and 3) and a multi-talker network remote microphone system each with five different signal levels (15 total conditions). Significant differences were found across all signal levels and technology conditions. Relative to the CI alone, sentence recognition improvements ranged from 14-23 percentage points with the adaptive multiple-microphone beamformer and 27-47 percentage points with the multi-talker network with superior performance for the latter remote microphone system. Both remote microphone systems significantly improved speech recognition in noise of CI recipients when listening in small group settings, but the multi-talker network provided superior performance.

Cochlear Implant Compression Optimization for Musical Sound Quality in MED-EL Users.

Variations in loudness are a fundamental component of the music listening experience. Cochlear implant (CI) processing, including amplitude compression, and a degraded auditory system may further degrade these loudness cues and decrease the enjoyment of music listening. This study aimed to identify optimal CI sound processor compression settings to improve music sound quality for CI users. Fourteen adult MED-EL CI recipients participated (Experiment No. 1: n = 17 ears; Experiment No. 2: n = 11 ears) in the study. A software application using a modified comparison category rating (CCR) test method allowed participants to compare and rate the sound quality of various CI compression settings while listening to 25 real-world music clips. The two compression settings studied were (1) Maplaw, which informs audibility and compression of soft level sounds, and (2) automatic gain control (AGC), which applies compression to loud sounds. For each experiment, one compression setting (Maplaw or AGC) was held at the default, while the other was varied according to the values available in the clinical CI programming software. Experiment No. 1 compared Maplaw settings of 500, 1000 (default), and 2000. Experiment No. 2 compared AGC settings of 2.5:1, 3:1 (default), and 3.5:1. In Experiment No. 1, the group preferred a higher Maplaw setting of 2000 over the default Maplaw setting of 1000 (p = 0.003) for music listening. There was no significant difference in music sound quality between the Maplaw setting of 500 and the default setting (p = 0.278). In Experiment No. 2, a main effect of AGC setting was found; however, no significant difference in sound quality ratings for pairwise comparisons were found between the experimental settings and the default setting (2.5:1 versus 3:1 at p = 0.546; 3.5:1 versus 3:1 at p = 0.059). CI users reported improvements in music sound quality with higher than default Maplaw or AGC settings. Thus, participants preferred slightly higher compression for music listening, with results having clinical implications for improving music perception in CI users.

A state-of-the-art implementation of a binaural cochlear-implant sound coding strategy inspired by the medial olivocochlear reflex

Cochlear implant (CI) users find it hard and effortful to understand speech in noise with current devices. Binaural CI sound processing inspired by the contralateral medial olivocochlear (MOC) reflex (an approach termed the ‘MOC strategy’) can improve speech-in-noise recognition for CI users. All reported evaluations of this strategy, however, disregarded automatic gain control (AGC) and fine‐structure (FS) processing, two standard features in some current CI devices. To better assess the potential of implementing the MOC strategy in contemporary CIs, here, we compare intelligibility with and without MOC processing in combination with linked AGC and FS processing. Speech reception thresholds (SRTs) were compared for an FS and a MOC-FS strategy for sentences in steady and fluctuating noises, for various speech levels, in bilateral and unilateral listening modes, and for multiple spatial configurations of the speech and noise sources. Word recall scores and verbal response times in a word recognition test (two proxies for listening effort) were also compared for the two strategies in quiet and in steady noise at 5 dB signal-to-noise ratio (SNR) and the individual SRT. In steady noise, mean SRTs were always equal or better with the MOC-FS than with the standard FS strategy, both in bilateral (the mean and largest improvement across spatial configurations and speech levels were 0.8 and 2.2 dB, respectively) and unilateral listening (mean and largest improvement of 1.7 and 2.1 dB, respectively). In fluctuating noise and in bilateral listening, SRTs were equal for the two strategies. Word recall scores and verbal response times were not significantly affected by the test SNR or the processing strategy. Results show that MOC processing can be combined with linked AGC and FS processing. Compared to using FS processing alone, combined MOC-FS processing can improve speech intelligibility in noise without affecting word recall scores or verbal response times.

Speech comprehension across multiple CI processor generations: Scene dependent signal processing.

ObjectivesIn clinical practice, characterization of speech comprehension for cochlear implant (CI) patients is typically administered by a set of suprathreshold measurements in quiet and in noise. This study investigates speech comprehension of the three most recent cochlear implant sound processors; CP810, CP910, and CP1000 (Cochlear Limited). To compare sound processor performance across generations and input dynamic range changes, the state‐of‐the art signal processing technologies available in each sound processor were enabled. Outcomes will be assessed across a range of stimulation intensities, and finally analyzed with respect to normal hearing listeners.MethodsIn a prospective study, 20 experienced postlingually deafened CI patients who received a Nucleus CI in the ENT department of the University Hospital of SH in Kiel were recruited. Speech comprehension was measured in quiet at 40, 50, and 65 dBSPL with monosyllabic words as well as by speech reception threshold for two‐digit numbers. In noise, speech reception thresholds were measured with the adaptive German matrix test with speech and noise in front.ResultsWe found that high levels of open‐set speech comprehension are achieved at suprathreshold presentation levels in quiet. However, results at lower test levels have remained mostly unchanged for tested sound processors with default dynamic range. Expanding the lower limit of the acoustic input dynamic range yields better speech comprehension at lower presentation levels. In noise the application of ForwardFocus improves the speech reception. Overall, a continuous improvement for speech perception across three generations of CI sound processors was found.ConclusionsFindings motivate further development of signal pre‐processing, an additional focus of clinical work on lower stimulation levels, and automation of ForwardFocus.Level of evidence2.

Recognition of Accented Speech by Cochlear-Implant Listeners: Benefit of Audiovisual Cues.

When auditory and visual speech information are presented together, listeners obtain an audiovisual (AV) benefit or a speech understanding improvement compared with auditory-only (AO) or visual-only (VO) presentations. Cochlear-implant (CI) listeners, who receive degraded speech input and therefore understand speech using primarily temporal information, seem to readily use visual cues and can achieve a larger AV benefit than normal-hearing (NH) listeners. It is unclear, however, if the AV benefit remains relatively large for CI listeners when trying to understand foreign-accented speech when compared with unaccented speech. Accented speech can introduce changes to temporal auditory cues and visual cues, which could decrease the usefulness of AV information. Furthermore, we sought to determine if the AV benefit was relatively larger in CI compared with NH listeners for both unaccented and accented speech. AV benefit was investigated for unaccented and Spanish-accented speech by presenting English sentences in AO, VO, and AV conditions to 15 CI and 15 age- and performance-matched NH listeners. Performance matching between NH and CI listeners was achieved by varying the number of channels of a noise vocoder for the NH listeners. Because of the differences in age and hearing history of the CI listeners, the effects of listener-related variables on speech understanding performance and AV benefit were also examined. AV benefit was observed for both unaccented and accented conditions and for both CI and NH listeners. The two groups showed similar performance for the AO and AV conditions, and the normalized AV benefit was relatively smaller for the accented than the unaccented conditions. In the CI listeners, older age was associated with significantly poorer performance with the accented speaker compared with the unaccented speaker. The negative impact of age was somewhat reduced by a significant improvement in performance with access to AV information. When auditory speech information is degraded by CI sound processing, visual cues can be used to improve speech understanding, even in the presence of a Spanish accent. The AV benefit of the CI listeners closely matched that of the NH listeners presented with vocoded speech, which was unexpected given that CI listeners appear to rely more on visual information to communicate. This result is perhaps due to the one-to-one age and performance matching of the listeners. While aging decreased CI listener performance with the accented speaker, access to visual cues boosted performance and could partially overcome the age-related speech understanding deficits for the older CI listeners.

Prediction of Individual Cochlear Implant Recipient Speech Perception With the Output Signal to Noise Ratio Metric.

A cochlear implant (CI) implements a variety of sound processing algorithms that seek to improve speech intelligibility. Typically, only a small number of parameter combinations are evaluated with recipients but the optimal configuration may differ for individuals. The present study evaluates a novel methodology which uses the output signal to noise ratio (OSNR) to predict complete psychometric functions that relate speech recognition to signal to noise ratio for individual CI recipients. Speech scores from sentence-in-noise tests in a "reference" condition were mapped to OSNR and a psychometric function was fitted. The reference variability was defined as the root mean square error between the reference scores and the fitted curve. To predict individual scores in a different condition, OSNRs in that condition were calculated and the corresponding scores were read from the reference psychometric function. In a retrospective experiment, scores were predicted for each condition and subject in three existing data sets of sentence scores. The prediction error was defined as the root mean square error between observed and predicted scores. In data set 1, sentences were mixed with 20 talker babble or speech weighted noise and presented at 65 dB sound pressure level (SPL). An adaptive test procedure was used. Sound processing was advanced combinatorial encoding (ACE, Cochlear Limited) and ACE with ideal binary mask processing, with five different threshold settings. In data set 2, sentences were mixed with speech weighted noise, street-side city noise or cocktail party noise and presented at 65 dB SPL. An adaptive test procedure was used. Sound processing was ACE and ACE with two different noise reduction schemes. In data set 3, sentences were mixed with four-talker babble at two input SNRs and presented at levels of 55-89 dB SPL. Sound processing utilised three different automatic gain control configurations. For data set 1, the median of individual prediction errors across all subjects, noise types and conditions, was 12% points, slightly better than the reference variability. The OSNR prediction method was inaccurate for the specific condition with a gain threshold of +10 dB. For data set 2, the median of individual prediction errors was 17% points and the reference variability was 11% points. For data set 3, the median prediction error was 9% points and the reference variability was 7% points. A Monte Carlo simulation found that the OSNR prediction method, which used reference scores and OSNR to predict individual scores in other conditions, was significantly more accurate (p < 0.01) than simply using reference scores as predictors. The results supported the hypothesis that the OSNR prediction method could accurately predict individual recipient scores for a range of algorithms and noise types, for all but one condition. The medians of the individual prediction errors for each data set were accurate within 6% points of the reference variability and compared favourably with prediction methodologies in other recent studies. Overall, the novel OSNR-based prediction method shows promise as a tool to assist researchers and clinicians in the development or fitting of CI sound processors.

Place-Pitch Interval Perception With a Cochlear Implant.

Pitch is poorly perceived by cochlear implant (CI) users. However, as it is not well understood how pitch is encoded with electric stimulation, improving pitch representation with a CI is challenging. Changes in place of stimulation along the cochlea have been described as changes in pitch and can be accurately ranked by CI users. However, it remains unknown if place-pitch can be used to encode musical intervals, which are a necessary attribute of pitch. The objective of these experiments is to determine if place-pitch coding can be used to represent musical intervals with a CI. In the first experiment, 10 CI users and 10 normal hearing (NH) controls were tested on their sensitivity to changes in the semitone spacing between each of the notes in the melody "Happy Birthday." The changes were implemented by uniformly expanding or compressing the frequency differences between each note in the melody. The participant's task was to scale how "out-of-tune" the melody was for various semitone spacing distortions. The notes were represented by pure-tones ≥440 Hz to minimize potential useful temporal information from the stimuli. A second experiment replicated the first experiment using single-sided deafened CI users allowing for a within-subject control. A third experiment verified that the CI users who participated in Experiment 1 were each able to determine pitch direction reliably. Unlike NH listeners, CI listeners often ranked all distortions of interval spacing similarly in both the first and second experiment, and no effect of interval spacing was detected across CI users. Some participants found distorted interval spacings to be less out-of-tune than the nominally correct interval spacings. However, these patterns were inconsistent across listeners. Although performance was better for the NH listeners, the third experiment demonstrated that the CI listeners were able to reliably identify changes in pitch direction from place-pitch coding. The data suggest that place-pitch intervals are not properly represented through a CI sound processor. Some limited support is found for place-pitch being useful for interval encoding as some participants demonstrated improved ratings for certain interval distortions. Presumably the interval representation for these participants could be improved by a change to the frequencies represented by each electrode. However, as these patterns vary across listeners, there is not a universal correction to frequency representation that will solve this issue. As results are similar for single-sided deafened CI users, the limitations in ratings are likely not limited by an eroded representation of the melody caused by an extended duration of deafness.

Effects of Electrode Location on Estimates of Neural Health in Humans with Cochlear Implants.

There are a number of psychophysical and electrophysiological measures that are correlated with SGN density in animal models, and these same measures can be performed in humans with cochlear implants (CIs). Thus, these measures are potentially applicable in humans for estimating the condition of the neural population (so called "neural health" or "cochlear health") at individual sites along the electrode array and possibly adjusting the stimulation strategy in the CI sound processor accordingly. Some measures used to estimate neural health in animals have included the electrically evoked compound potential (ECAP), psychophysical detection thresholds, and multipulse integration (MPI). With regard to ECAP measures, it has been shown that the change in the ECAP response as a function of increasing the stimulus interphase gap ("IPG Effect") also reflects neural density in implanted animals. These animal studies have typically been conducted using preparations in which the electrode was in a fixed position with respect to the neural population, whereas in human cochlear implant users, the position of individual electrodes varies widely within an electrode array and also across subjects. The current study evaluated the effects of electrode location in the implanted cochlea (specifically medial-lateral location) on various electrophysiological and psychophysical measures in eleven human subjects. The results demonstrated that some measures of interest, specifically ECAP thresholds, psychophysical detection thresholds, and ECAP amplitude-growth function (AGF) linear slope, were significantly related to the distances between the electrode and mid-modiolar axis (MMA). These same measures were less strongly related or not significantly related to the electrode to medial wall (MW) distance. In contrast, neither the IPG Effect for the ECAP AGF slope or threshold, nor the MPI slopes were significantly related to MMA or MW distance from the electrodes. These results suggest that "within-channel" estimates of neural health such as the IPG Effect and MPI slope might be more suitable for estimating nerve condition in humans for clinical application since they appear to be relatively independent of electrode position.

The efficacy of microphone directionality in improving speech recognition in noise for three commercial cochlear-implant systems

Objectives: To investigate the effect of fixed and adaptive microphone directionality on speech reception threshold (SRT) in noise when compared to omnidirectional mode in unilateral cochlear-implant (CI) use for three different CI systems.Methods: Twenty-four CI recipients with bilateral severe-to-profound hearing loss participated in the study. Eight recipients of each CI system were enrolled, and their SRT in noise was measured when the speech and noise signals were co-located in the front to serve as a baseline. The acute effect of different microphone directionalities on SRT in noise was measured with the noise emanating at 90° in the horizontal plane from the side of the CI sound processor (S0NCI).Results: When compared to the baseline condition, the individual data revealed fairly similar patterns within each CI system. In the S0NCI condition, the average improvement in SRT in noise for fixed and adaptive directionalities over the omnidirectional mode was statistically significant and ranged from 1.2 to 6.0 dB SNR and from 3.7 to 12.7 dB SNR depending on the CI system, respectively.Discussion: Directional microphones significantly improve SRT in noise for all three CI systems. However, relatively large differences were observed in the directional microphone efficacy between CI systems.

Searching for the Sound of a Cochlear Implant: Evaluation of Different Vocoder Parameters by Cochlear Implant Users With Single-Sided Deafness

Cochlear implantation in subjects with single-sided deafness (SSD) offers a unique opportunity to directly compare the percepts evoked by a cochlear implant (CI) with those evoked acoustically. Here, nine SSD-CI users performed a forced-choice task evaluating the similarity of speech processed by their CI with speech processed by several vocoders presented to their healthy ear. In each trial, subjects heard two intervals: their CI followed by a certain vocoder in Interval 1 and their CI followed by a different vocoder in Interval 2. The vocoders differed either (i) in carrier type—(sinusoidal [SINE], bandfiltered noise [NOISE], and pulse-spreading harmonic complex) or (ii) in frequency mismatch between the analysis and synthesis frequency ranges—(no mismatch, and two frequency-mismatched conditions of 2 and 4 equivalent rectangular bandwidths [ERBs]). Subjects had to state in which of the two intervals the CI and vocoder sounds were more similar. Despite a large intersubject variability, the PSHC vocoder was judged significantly more similar to the CI than SINE or NOISE vocoders. Furthermore, the No-mismatch and 2-ERB mismatch vocoders were judged significantly more similar to the CI than the 4-ERB mismatch vocoder. The mismatch data were also interpreted by comparing spiral ganglion characteristic frequencies with electrode contact positions determined from postoperative computed tomography scans. Only one subject demonstrated a pattern of preference consistent with adaptation to the CI sound processor frequency-to-electrode allocation table and two subjects showed possible partial adaptation. Those subjects with adaptation patterns presented overall small and consistent frequency mismatches across their electrode arrays.

Techniques for Remotely Programming Children With Cochlear Implants Using Pediatric Audiological Methods via Telepractice.

The purpose of this report is to describe the equipment setup and techniques for successfully testing behavioral thresholds in young children with cochlear implants (CIs) using telepractice. We will also discuss challenges associated with pediatric CI programming that are unique to the use of distance technology, and we will describe ways to overcome those challenges. Last, we will review the results from 2 recent studies specifically targeted toward testing behavioral thresholds in young children with CIs. Conditioned play audiometry or visual reinforcement audiometry was used to measure behavioral thresholds (T levels) for 35 young children with CIs (n = 19 for conditioned play audiometry and n = 16 for visual reinforcement audiometry). Participants were tested in the traditional in-person condition and in the remote condition using an AB-BA study design over 2 visits. There was no significant difference in T levels between the in-person and remote conditions, indicating that it is feasible to test young children using conventional pediatric testing procedures via remote technology. The primary challenges encountered were in regard to proper camera and video monitor placement at the remote site and the timing of communication between the audiologist and test assistant. The results from studies to date suggest that distance technology can be used successfully to program CI sound processors for young children using standard, age-appropriate testing techniques. The alternative of remote testing has substantial implications for reducing time and travel burdens for families, potentially leading to the construction of appropriate maps for young children with CIs in a timelier manner.

An Evaluation of Output Signal to Noise Ratio as a Predictor of Cochlear Implant Speech Intelligibility.

Cochlear implant (CI) sound processing strategies are usually evaluated in clinical studies involving experienced implant recipients. Metrics which estimate the capacity to perceive speech for a given set of audio and processing conditions provide an alternative means to assess the effectiveness of processing strategies. The aim of this research was to assess the ability of the output signal to noise ratio (OSNR) to accurately predict speech perception. It was hypothesized that compared with the other metrics evaluated in this study (1) OSNR would have equivalent or better accuracy and (2) OSNR would be the most accurate in the presence of variable levels of speech presentation. For the first time, the accuracy of OSNR as a metric which predicts speech intelligibility was compared, in a retrospective study, with that of the input signal to noise ratio (ISNR) and the short-term objective intelligibility (STOI) metric. Because STOI measured audio quality at the input to a CI sound processor, a vocoder was applied to the sound processor output and STOI was also calculated for the reconstructed audio signal (vocoder short-term objective intelligibility [VSTOI] metric). The figures of merit calculated for each metric were Pearson correlation of the metric and a psychometric function fitted to sentence scores at each predictor value (Pearson sigmoidal correlation [PSIG]), epsilon insensitive root mean square error (RMSE*) of the psychometric function and the sentence scores, and the statistical deviance of the fitted curve to the sentence scores (D). Sentence scores were taken from three existing data sets of Australian Sentence Tests in Noise results. The AuSTIN tests were conducted with experienced users of the Nucleus CI system. The score for each sentence was the proportion of morphemes the participant correctly repeated. In data set 1, all sentences were presented at 65 dB sound pressure level (SPL) in the presence of four-talker Babble noise. Each block of sentences used an adaptive procedure, with the speech presented at a fixed level and the ISNR varied. In data set 2, sentences were presented at 65 dB SPL in the presence of stationary speech weighted noise, street-side city noise, and cocktail party noise. An adaptive ISNR procedure was used. In data set 3, sentences were presented at levels ranging from 55 to 89 dB SPL with two automatic gain control configurations and two fixed ISNRs. For data set 1, the ISNR and OSNR were equally most accurate. STOI was significantly different for deviance (p = 0.045) and RMSE* (p < 0.001). VSTOI was significantly different for RMSE* (p < 0.001). For data set 2, ISNR and OSNR had an equivalent accuracy which was significantly better than that of STOI for PSIG (p = 0.029) and VSTOI for deviance (p = 0.001), RMSE*, and PSIG (both p < 0.001). For data set 3, OSNR was the most accurate metric and was significantly more accurate than VSTOI for deviance, RMSE*, and PSIG (all p < 0.001). ISNR and STOI were unable to predict the sentence scores for this data set. The study results supported the hypotheses. OSNR was found to have an accuracy equivalent to or better than ISNR, STOI, and VSTOI for tests conducted at a fixed presentation level and variable ISNR. OSNR was a more accurate metric than VSTOI for tests with fixed ISNRs and variable presentation levels. Overall, OSNR was the most accurate metric across the three data sets. OSNR holds promise as a prediction metric which could potentially improve the effectiveness of sound processor research and CI fitting.

An Investigation of the Effect of AGC Gain on the Output Signal to Noise Ratio in Cochlear Implant Sound Processing.

Measurement of speech intelligibility of cochlear implant (CI) recipients is typically carried out with a speech-innoise test procedure. Metrics which predict speech intelligibility can pre-screen new sound processing strategies prior to comprehensive testing with human subjects.The Output Signal to Noise Ratio (OSNR) metric calculates the Signal to Noise Ratio (SNR) which is present at the CI sound processor output. Watkins et al. (2018) found OSNR was an accurate predictor of speech intelligibility that could predict intelligibility in scenarios where other predictors could not.The current study investigated the effect of the sound processor automatic gain control (AGC) on OSNR and a simplified metric, Separate gain SNR (SSNR), which calculated the SNR at the CI output, assuming no interaction between the signal and noise in the sound processor. Prediction accuracy of OSNR was compared to that of Input SNR and SSNR.It was found that AGC-induced distortion and SNR degradation in speech gaps worsened OSNR. For scenarios with significant non-linear, time-varying processing, OSNR was the most accurate prediction metric. SSNR was found to be an inaccurate predictor.

Verification Protocol for Signal Transparency Using the Cochlear Mini-Microphone 2+ and Digital Modulation Transmitter and Receiver with Cochlear Implants.

Guidelines established by the American Academy of Audiology (AAA) currently recommend behavioral testing when fitting frequency-modulated (FM) systems to individuals with cochlear implants (CIs). A protocol for completing electroacoustic measures on CI sound processors has not yet been established or validated when fitting either FM or digital-modulated (DM) systems, mini microphones, or mini microphones coupled to DM systems. In response, professionals have used or altered the AAA (2008) electroacoustic verification steps for fitting FM systems to hearing aids when fitting FM/DM systems, mini microphones, or mini microphones coupled to FM/DM systems to CI sound processors. The purpose of this research is to determine if the electroacoustic verification guidelines established by AAA (2008) for fitting FM systems to hearing aids are feasible and verifiable when fitting mini microphones and mini microphones coupled to DM systems to CI sound processors. Electroacoustic measures were conducted on 51 Cochlear Nucleus 6/CP910 sound processors, one Cochlear Wireless Mini Microphone 2+ (MM2+), and one Phonak DM System (one Roger Inspiro transmitter and one Roger X receiver) using an adapted AAA (2008) protocol (Nair et al, 2017). Phonak's recommended default receiver gain setting was used with the Roger X receiver and adjusted if necessary to achieve transparency. Transparency refers to when the signal output of the device is the same when coupled and when not coupled to remote microphone technology. Electroacoustic measures were conducted on 51 Cochlear Nucleus 6/CP910 sound processors. In this study, the 51 Cochlear Nucleus 6/CP910 sound processors were either streaming to the Cochlear MM2+ or streaming to the MM2+ coupled to a Phonak DM system. In a clinical setting, using the AAA (2008) protocol for electroacoustic measurements when fitting FM systems to hearing aids, electroacoustic measurements using various equipment (MM2+ and Phonak DM system) were performed on 51 Cochlear Nucleus 6/CP910 sound processors using the Audioscan Verifit to determine transparency and verify DM advantage, comparing speech inputs (65 dB SPL) in an effort to achieve equal outputs. If transparency was not achieved when the CI sound processor was streaming to the MM2+ coupled to the Phonak DM system at the default receiver gain, adjustments were made to the Roger X receiver's gain. The integrity of the signal was monitored with the manufacturer's monitor earphones. Using the AAA (2008) hearing aid protocol, when the Cochlear Nucleus 6/CP910 sound processor was streaming to the Cochlear MM2+, transparency was achieved for 50 of 51 CI sound processors. Again, using the AAA (2008) protocol when the Cochlear Nucleus 6/CP910 sound processor was streaming to the Cochlear MM2+ coupled to the Phonak DM system at Phonak's recommended default receiver gain, 28 sound processors achieved transparency. After the receiver gain was adjusted, the remaining 23 sound processors met transparency. Electroacoustic measurements and transparency can be achieved for CI sound processors coupled to either a MM2+ only or to a MM2+ and a DM system by adapting the AAA (2008) guidelines.

Verification of a Proposed Clinical Electroacoustic Test Protocol for Personal Digital Modulation Receivers Coupled to Cochlear Implant Sound Processors.

Guidelines established by the AAA currently recommend behavioral testing when fitting frequency modulated (FM) systems to individuals with cochlear implants (CIs). A protocol for completing electroacoustic measures has not yet been validated for personal FM systems or digital modulation (DM) systems coupled to CI sound processors. In response, some professionals have used or altered the AAA electroacoustic verification steps for fitting FM systems to hearing aids when fitting FM systems to CI sound processors. More recently steps were outlined in a proposed protocol. The purpose of this research is to review and compare the electroacoustic test measures outlined in a 2013 article by Schafer and colleagues in the Journal of the American Academy of Audiology titled "A Proposed Electroacoustic Test Protocol for Personal FM Receivers Coupled to Cochlear Implant Sound Processors" to the AAA electroacoustic verification steps for fitting FM systems to hearing aids when fitting DM systems to CI users. Electroacoustic measures were conducted on 71 CI sound processors and Phonak Roger DM systems using a proposed protocol and an adapted AAA protocol. Phonak's recommended default receiver gain setting was used for each CI sound processor manufacturer and adjusted if necessary to achieve transparency. Electroacoustic measures were conducted on Cochlear and Advanced Bionics (AB) sound processors. In this study, 28 Cochlear Nucleus 5/CP810 sound processors, 26 Cochlear Nucleus 6/CP910 sound processors, and 17 AB Naida CI Q70 sound processors were coupled in various combinations to Phonak Roger DM dedicated receivers (25 Phonak Roger 14 receivers-Cochlear dedicated receiver-and 9 Phonak Roger 17 receivers-AB dedicated receiver) and 20 Phonak Roger Inspiro transmitters. Employing both the AAA and the Schafer et al protocols, electroacoustic measurements were conducted with the Audioscan Verifit in a clinical setting on 71 CI sound processors and Phonak Roger DM systems to determine transparency and verify FM advantage, comparing speech inputs (65 dB SPL) in an effort to achieve equal outputs. If transparency was not achieved at Phonak's recommended default receiver gain, adjustments were made to the receiver gain. The integrity of the signal was monitored with the appropriate manufacturer's monitor earphones. Using the AAA hearing aid protocol, 50 of the 71 CI sound processors achieved transparency, and 59 of the 71 CI sound processors achieved transparency when using the proposed protocol at Phonak's recommended default receiver gain. After the receiver gain was adjusted, 3 of 21 CI sound processors still did not meet transparency using the AAA protocol, and 2 of 12 CI sound processors still did not meet transparency using the Schafer et al proposed protocol. Both protocols were shown to be effective in taking reliable electroacoustic measurements and demonstrate transparency. Both protocols are felt to be clinically feasible and to address the needs of populations that are unable to reliably report regarding the integrity of their personal DM systems.

Feasibility of an implanted microphone for cochlear implant listening.

This study aimed at evaluating the feasibility of an implanted microphone for cochlear implants (CI) by comparison of hearing outcomes, sound quality and patient satisfaction of a subcutaneous microphone to a standard external microphone of a behind-the-ear sound processor. In this prospective feasibility study with a within-subject repeated measures design comparing the microphone modalities, ten experienced adult unilateral CI users received an implantable contralateral subcutaneous microphone attached to a percutaneous plug. The signal was pre-processed and fed into their CI sound processor. Subjects compared listening modes at home for a period of up to 4months. At the end of the study the microphone was explanted. Aided audiometric thresholds, speech understanding in quiet, and sound quality questionnaires were assessed. On average thresholds (250, 500, 750, 1k, 2k, 3k, 4k and 6kHz) with the subcutaneous microphone were 44.9dB, compared to 36.4dB for the external mode. Speech understanding on sentences in quiet was high, within approximately 90% of performance levels compared to hearing with an external microphone. Body sounds were audible but not annoying to almost all subjects. This feasibility study with a research device shows significantly better results than previous studies with implanted microphones. This is attributed to technology enhancements and careful fitting. Listening effort was somewhat increased with an implanted microphone. Under good sound conditions, speech performance is nearly similar to that of external microphones demonstrating that an implanted microphone is feasible in a range of normal listening conditions.