Search

Purpose: For bilaterally implanted patients, the automatic gain control (AGC) in both left and right cochlear implant (CI) processors is usually neither linked nor synchronized. At high AGC compression ratios, this lack of coordination between the two processors can distort interaural level differences, the only useful interaural difference cue available to CI patients. This study assessed the improvement, if any, in the utility of interaural level differences for sound source localization in the frontal hemifield when AGCs were synchronized versus independent and when listeners were stationary versus allowed to move their heads. Method: Sound source identification of broadband noise stimuli was tested for seven bilateral CI patients using 13 loudspeakers in the frontal hemifield, under conditions where AGCs were linked and unlinked. For half the conditions, patients remained stationary; in the other half, they were encouraged to rotate or reorient their heads within a range of approximately ± 30° during sound presentation. Results: In general, those listeners who already localized reasonably well with independent AGCs gained the least from AGC synchronization, perhaps because there was less room for improvement. Those listeners who performed worst with independent AGCs gained the most from synchronization. All listeners performed as well or better with synchronization than without; however, intersubject variability was high. Head movements had little impact on the effectiveness of synchronization of AGCs. Conclusion: Synchronization of AGCs offers one promising strategy for improving localization performance in the frontal hemifield for bilaterally implanted CI patients.

Purpose: The aims of this exploratory study were (a) to assess common terms used to describe cochlear implant (CI) sound quality by patients fit with conventional CIs and (b) to compare those descriptors to previously obtained acoustic matches to CI sound quality created by single-sided deaf (SSD) patients for their normal-hearing ear. Method: CI patients fit with Advanced Bionics (AB; n = 89), Cochlear Corporation (n = 86), and MED-EL (n = 80) implants were the participants. The patients filled out a questionnaire about CI sound quality for two time points: For the time near activation (T1) from memory and at the time of filling out the questionnaire (T2). The mean CI experience at T2 for the three groups ranged from 4 to 8 years. The questionnaire was composed of 25 adjectives describing sound quality. Results: For T1, the most commonly used descriptors were Computer-like, Treble-y, Metallic, and Mickey Mouse--like. A superordinate category of HiPitched (High Pitched) gathered significantly more responses from patients with shorter electrode arrays (AB and Cochlear) than patients with longer arrays (MED-EL). At T2, the most common descriptor was Clear and was chosen by approximately two thirds of the patients. The between-group differences in responses to items in the HiPitched category, present at T1, were absent at T2. Conclusions: The questionnaire data from conventional CI patients differs from previous sound matching data collected from SSD-CI patients. Alterations to the spectral composition of the signal are less salient to experienced conventional patients than to experienced SSD-CI patients. This is likely due to the absence, for conventional patients, of an exemplar in an NH ear against which to judge CI sound quality. [ABSTRACT FROM AUTHOR]

Purpose: Our aim was to make audible for normal-hearing listeners the Mickey Mouse™ sound quality of cochlear implants (CIs) often found following device activation. Method: The listeners were 3 single-sided deaf patients fit with a CI and who had 6 months or less of CI experience. Computed tomography imaging established the location of each electrode contact in the cochlea and allowed an estimate of the place frequency of the tissue nearest each electrode. For the most apical electrodes, this estimate ranged from 650 to 780 Hz. To determine CI sound quality, a clean signal (a sentence) was presented to the CI ear via a direct connect cable and candidate, and CI-like signals were presented to the ear with normal hearing via an insert receiver. The listeners rated the similarity of the candidate signals to the sound of the CI on a 1- to 10-point scale, with 10 being a complete match. Results: To make the match to CI sound quality, all 3 patients need an upshift in formant frequencies (300-800 Hz) and a metallic sound quality. Two of the 3 patients also needed an upshift in voice pitch (10-80 Hz) and a muffling of sound quality. Similarity scores ranged from 8 to 9.7. Conclusion: The formant frequency upshifts, fundamental frequency upshifts, and metallic sound quality experienced by the listeners can be linked to the relatively basal locations of the electrode contacts and short duration experience with their devices. The perceptual consequence was not the voice quality of Mickey Mouse™ but rather that of Munchkins in "The Wizard of Oz" for whom both formant frequencies and voice pitch were upshifted.

Purpose: The primary purpose of this study was to assess speech understanding in quiet and in diffuse noise for adult cochlear implant (CI) recipients utilizing bimodal hearing or bilateral CIs. Our primary hypothesis was that bilateral CI recipients would demonstrate less effect of source azimuth in the bilateral CI condition due to symmetric interaural head shadow. Method: Sentence recognition was assessed for adult bilateral (n = 25) CI users and bimodal listeners (n = 12) in three conditions: (1) source location certainty regarding fixed target azimuth, (2) source location uncertainty regarding roving target azimuth, and (3) Condition 2 repeated, allowing listeners to turn their heads, as needed. Results: (a) Bilateral CI users exhibited relatively similar performance regardless of source azimuth in the bilateral CI condition; (b) bimodal listeners exhibited higher performance for speech directed to the better hearing ear even in the bimodal condition; (c) the unilateral, better ear condition yielded higher performance for speech presented to the better ear versus speech to the front or to the poorer ear; (d) source location certainty did not affect speech understanding performance; and (e) head turns did not improve performance. The results confirmed our hypothesis that bilateral CI users exhibited less effect of source azimuth than bimodal listeners. That is, they exhibited similar performance for speech recognition irrespective of source azimuth, whereas bimodal listeners exhibited significantly poorer performance with speech originating from the poorer hearing ear (typically the nonimplanted ear). Conclusions: Bilateral CI users overcame ear and source location effects observed for the bimodal listeners. Bilateral CI users have access to head shadow on both sides, whereas bimodal listeners generally have interaural asymmetry in both speech understanding and audible bandwidth limiting the head shadow benefit obtained from the poorer ear (generally the nonimplanted ear). In summary, we found that, in conditions with source location uncertainty and increased ecological validity, bilateral CI performance was superior to bimodal listening.

Cochlear implant (CI) systems differ in terms of electrode design and signal processing. It is likely that patients fit with different implant systems will experience different percepts when presented speech via their implant. The sound quality of speech can be evaluated by asking single-sided-deaf (SSD) listeners fit with a cochlear implant (CI) to modify clean signals presented to their typically hearing ear to match the sound quality of signals presented to their CI ear. In this paper, we describe very close matches to CI sound quality, i.e., similarity ratings of 9.5 to 10 on a 10-point scale, by ten patients fit with a 28 mm electrode array and MED EL signal processing. The modifications required to make close approximations to CI sound quality fell into two groups: One consisted of a restricted frequency bandwidth and spectral smearing while a second was characterized by a wide bandwidth and no spectral smearing. Both sets of modifications were different from those found for patients with shorter electrode arrays who chose upshifts in voice pitch and formant frequencies to match CI sound quality. The data from matching-based metrics of CI sound quality document that speech sound-quality differs for patients fit with different CIs and among patients fit with the same CI. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this article is to summarize recent published and unpublished research from our 2 laboratories on improving speech understanding in complex listening environments by listeners fit with cochlear implants (CIs). Method: CI listeners were tested in 2 listening environments. One was a simulation of a restaurant with multiple, diffuse noise sources, and the other was a cocktail party with 2 spatially separated point sources of competing speech. At issue was the value of the following sources of information, or interventions, on speech understanding: (a) visual information, (b) adaptive beamformer microphones and remote microphones, (c) bimodal fittings, that is, a CI and contralateral low-frequency acoustic hearing, (d) hearing preservation fittings, that is, a CI with preserved low-frequency acoustic in the same ear plus low-frequency acoustic hearing in the contralateral ear, and (e) bilateral CIs. Results: A remote microphone provided the largest improvement in speech understanding. Visual information and adaptive beamformers ranked next, while bimodal fittings, bilateral fittings, and hearing preservation provided significant but less benefit than the other interventions or sources of information. Only bilateral CIs allowed listeners high levels of speech understanding when signals were roved over the frontal plane. Conclusions: The evidence supports the use of bilateral CIs and hearing preservation surgery for best speech understanding in complex environments. These fittings, when combined with visual information and microphone technology, should lead to high levels of speech understanding by CI patients in complex listening environments.

Purpose: The aim of this experiment was to compare, for patients with cochlear implants (CIs), the improvement for speech understanding in noise provided by a monaural adaptive beamformer and for two interventions that produced bilateral input (i.e., bilateral CIs and hearing preservation [HP] surgery). Method: Speech understanding scores for sentences were obtained for 10 listeners fit with a single CI. The listeners were tested with and without beamformer activated in a "cocktail party" environment with spatially separated target and maskers. Data for 10 listeners with bilateral CIs and 8 listeners with HP CIs were taken from Loiselle, Dorman, Yost, Cook, and Gifford (2016), who used the same test protocol. Results: The use of the beamformer resulted in a 31 percentage point improvement in performance; in bilateral CIs, an 18 percentage point improvement; and in HP CIs, a 20 percentage point improvement. Conclusion: A monaural adaptive beamformer can produce an improvement in speech understanding in a complex noise environment that is equal to, or greater than, the improvement produced by bilateral CIs and HP surgery.

Purpose: Five experiments probed auditory-visual (AV) understanding of sentences by users of cochlear implants (CIs). Method: Sentence material was presented in auditory (A), visual (V), and AV test conditions to listeners with normal hearing and CI users. Results: (a) Most CI users report that most of the time, they have access to both A and V information when listening to speech. (b) CI users did not achieve better scores on a task of speechreading than did listeners with normal hearing. (c) Sentences that are easy to speechread provided 12 percentage points more gain to speech understanding than did sentences that were difficult. (d) Ease of speechreading for sentences is related to phrase familiarity. (e) Users of bimodal CIs benefit from low-frequency acoustic hearing even when V cues are available, and a second CI adds to the benefit of a single CI when V cues are available. (f) V information facilitates lexical segmentation by improving the recognition of the number of syllables produced and the relative strength of these syllables. Conclusions: Our data are consistent with the view that V information improves CI users' ability to identify syllables in the acoustic stream and to recognize their relative juxtaposed strengths. Enhanced syllable resolution allows better identification of word onsets, which, when combined with place-of-articulation information from visible consonants, improves lexical access.

Purpose: To assess the role of interaural time differences and interaural level differences in (a) sound-source localization, and (b) speech understanding in a cocktail party listening environment for listeners with bilateral cochlear implants (CIs) and for listeners with hearing-preservation CIs. Methods: Eleven bilateral listeners with MED-EL (Durham, NC) CIs and 8 listeners with hearing-preservation CIs with symmetrical low frequency, acoustic hearing using the MED-EL or Cochlear device were evaluated using 2 tests designed to task binaural hearing, localization, and a simulated cocktail party. Access to interaural cues for localization was constrained by the use of low-pass, high-pass, and wideband noise stimuli. Results: Sound-source localization accuracy for listeners with bilateral CIs in response to the high-pass noise stimulus and sound-source localization accuracy for the listeners with hearing-preservation CIs in response to the low-pass noise stimulus did not differ significantly. Speech understanding in a cocktail party listening environment improved for all listeners when interaural cues, either interaural time difference or interaural level difference, were available. Conclusions: The findings of the current study indicate that similar degrees of benefit to sound-source localization and speech understanding in complex listening environments are possible with 2 very different rehabilitation strategies: the provision of bilateral CIs and the preservation of hearing.

Objective: Our aim was to determine the effect of acute changes in cochlear place of stimulation on cochlear implant (CI) sound quality.Design: In Experiment 1, 5 single-sided deaf (SSD) listeners fitted with a long (28-mm) electrode array were tested. Basal shifts in place of stimulation were implemented by turning off the most apical electrodes and reassigning the filters to more basal electrodes. In Experiment 2, 2 SSD patients fitted with a shorter (16.5-mm) electrode array were tested. Both basal and apical shifts in place of stimulation were implemented. The apical shifts were accomplished by current steering and creating a virtual place of stimulation more apical that that of the most apical electrode.Results: Listeners matched basal shifts by shifting, in the normal-hearing ear, the overall spectrum up in frequency and/or increasing voice pitch (F0). Listeners matched apical shifts by shifting down the overall frequency spectrum in the normal-hearing ear.Conclusion: One factor determining CI voice quality is the location of stimulation along the cochlear partition. [ABSTRACT FROM AUTHOR]

Background Both the Roger remote microphone and on-ear, adaptive beamforming technologies (e.g., Phonak UltraZoom) have been shown to improve speech understanding in noise for cochlear implant (CI) listeners when tested in audio-only (A-only) test environments. Purpose Our aim was to determine if adult and pediatric CI recipients benefited from these technologies in a more common environment--one in which both audio and visual cues were available and when overall performance was high. Study Sample Ten adult CI listeners (Experiment 1) and seven pediatric CI listeners (Experiment 2) were tested. Design Adults were tested in quiet and in two levels of noise (level 1 and level 2) in Aonly and audio-visual (AV) environments. There were four device conditions: (1) an ear canal-level, omnidirectional microphone (T-mic) in quiet, (2) the T-mic in noise, (3) an adaptive directional mic (UltraZoom) in noise, and (4) a wireless, remote mic (Roger Pen) in noise. Pediatric listeners were tested in quiet and in level 1 noise in A-only and AV environments. The test conditions were: (1) a behind-the-ear level omnidirectional mic (processor mic) in quiet, (2) the processor mic in noise, (3) the T-mic in noise, and (4) the Roger Pen in noise. Data Collection and Analyses In each test condition, sentence understanding was assessed (percent correct) and ease of listening ratings were obtained. The sentence understanding data were entered into repeated-measures analyses of variance. Results For both adult and pediatric listeners in the AV test conditions in level 1 noise, performance with the Roger Pen was significantly higher than with the T-mic. For both populations, performance in level 1 noisewith the Roger Pen approached the level of baseline performance in quiet. Ease of listening in noise was rated higher in the Roger Pen conditions than in the T-mic or processor mic conditions in both A-only and AV test conditions. Conclusion The Roger remote mic and on-ear directional mic technologies benefit both speech understanding and ease of listening in a realistic laboratory test environment and are likely do the same in real-world listening environments. [ABSTRACT FROM AUTHOR]

Objective: Our primary aim was to determine, in a simulation of a crowded restaurant, the value to speech understanding of (i) a unilateral cochlear implant (CI), (ii) a CI plus CROS (contralateral routing of signals) aid system and (iii) bilateral CIs when tested with and without beamforming microphones.Design: The listeners were 7 CI listeners who had used bilateral CIs for an average of 9 years. The listeners were tested with three device configurations (bilateral CI, unilateral CI + CROS, and unilateral CI), two signal processing conditions (without and with beamformers) and with speech either from +90°, -90°, or from the front. Speech understanding scores for the TIMIT sentences were obtained in the 8-loudspeaker R-SPACETM test environment - an environment which simulates listening in a crowded restaurant.Results: In the unilateral condition, speech understanding, relative to speech directed to the CI ear, fell by 17% when speech was from the front and fell 28% when speech was to the side opposite the CI. These deficits were overcome with both CI-CROS and bilateral CIs, and scores for the two devices did not differ significantly for any location of speech input. Beamformer microphones improved speech understanding for speech from the front and depressed speech understanding for speech from the sides for all device configurations. Patients with bilateral CIs and beamformers achieved slightly, but significantly, higher scores for speech from the front than patients with CI-CROS and beamformers.Conclusions: CI-CROS is a valuable addition to the hardware options available to patients fit with a single CI. For patients fit with bilateral CIs, bilateral beamformers are a valuable addition in the condition of speech coming from in front of the listener. The small differences in performance in the CI-CROS and bilateral CI conditions suggest that patient preference for bilateral CIs is based largely on factors other than speech understanding in noise. [ABSTRACT FROM AUTHOR]

Unilateral severe-to-profound sensorineural hearing loss (SNHL), also known as single sided deafness (SSD), is a problem that affects both children and adults, and can have severe and detrimental effects on multiple aspects of life including music appreciation, speech understanding in noise, speech and language acquisition, performance in the classroom and/or the workplace, and quality of life. Additionally, the loss of binaural hearing in SSD patients affects those processes that rely on two functional ears including sound localization, binaural squelch and summation, and the head shadow effect. Over the last decade, there has been increasing interest in cochlear implantation for SSD to restore binaural hearing. Early data are promising that cochlear implantation for SSD can help to restore binaural functionality, improve quality of life, and may faciliate reversal of neuroplasticity related to auditory deprivation in the pediatric population. Additionally, this new patient population has allowed researchers the opportunity to investigate the age-old question "what does a cochlear implant (CI) sound like?."