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The AzBio sentence test is widely used to assess speech perception pre- and post-cochlear implantation. This study created and validated a Hebrew version of AzBio (HeBio) and tested its intelligibility amidst background noise., In Experiment 1, 1,000 recorded Hebrew sentences were presented via five-channel vocoder to 10 normal hearing (NH) listeners for intelligibility testing. In Experiment 2, HeBio lists were presented to 25 post-lingual cochlear implant (CI) users amidst four-talker babble noise (4TBN) or in quiet, along with one-syllable word test. In Experiment 3, 20 NH listeners were presented with eight HeBio lists in two noise conditions [4TBN, speech shaped noise (SSN)] and four SNRs (+3, 0 dB, -3 dB, -6 dB)., HeBio lists (33) produced 82% average understanding, no inter-list intelligibility differences among NH, and equal intelligibility for CI users. One-syllable words predicted 67% of the variance in HeBio among CI users. Higher intelligibility was found for SSN than for 4TBN, and the mean speech receptive threshold (SRT) was more negative for SSN than for 4TBN., HeBio results were similar to AzBio. Results obtained with two noise types were as expected. HeBio is recommended for evaluation of different populations in quiet and noise.

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. Supplemental Material https://doi.org/10.23641/asha.14681412.

Objective: To create and validate a Spanish sentence test for evaluation of speech understanding of Spanish-speaking listeners with hearing loss or cochlear implants (CI)., Study Design: Two thousand sentences were recorded from two male and two female speakers. The average intelligibility of each sentence was estimated as the mean score achieved by five listeners presented with a five-channel cochlear implant simulation. The mean scores of each sentence were used to construct 42 lists of 20 sentences with similar mean scores. List equivalency was then validated by presenting all lists to 10 CI users and in a 2-list comparison in a clinical setting to 38 CI patients., Setting: Tertiary referral center., Patients: Normal-hearing listeners (n = 5), CI users in a research study (n = 10), and CI patients (n = 38) in routine clinical follow-up., Intervention: Multiple sentence lists from a newly minted speech perception test., Main Outcome Measures: List intelligibility and equivalence across sentence lists., Results: Forty-two lists of sentences were equivalent when all lists were presented in random order to 10 adult CI recipients. The variability of scores observed on lists presented to the same listener in the same condition was captured using a binomial distribution model based on a 40-item list for 38 adult implant recipients., Conclusion: The Spanish AzBio Sentence Test includes 42 lists of 20 sentences. These sentences are roughly equivalent in terms of overall difficulty and confidence limits have been provided to assess the significance of variability in list scores observed within or across conditions. These materials will be of benefit when assessing native Spanish speakers in both research and clinical settings.

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 A-only 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 noise with 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., Competing Interests: Dr. Dorman reports grants and personal fees from Advanced Bionics, during the conduct of the study; grants and personal fees from MED-EL Corporation, outside the submitted work. Dr. Agrawal reports personal fees from Advanced Bionics, during the conduct of the study. Dr. Natale has nothing to disclose., (American Academy of Audiology. This article is published by Thieme.)

Background: Previous research has found that when the location of a talker was varied and an auditory prompt indicated the location of the talker, the addition of visual information produced a significant and large improvement in speech understanding for listeners with bilateral cochlear implants (CIs) but not with a unilateral CI. Presumably, the sound-source localization ability of the bilateral CI listeners allowed them to orient to the auditory prompt and benefit from visual information for the subsequent target sentence., Purpose: The goal of this project was to assess the robustness of previous research by using a different test environment, a different CI, different test material, and a different response measure., Research Design: Nine listeners fit with bilateral CIs were tested in a simulation of a crowded restaurant. Auditory-visual (AV) sentence material was presented from loudspeakers and video monitors at 0, +90, and -90 degrees. Each trial started with the presentation of an auditory alerting phrase from one of the three target loudspeakers followed by an AV target sentence from that loudspeaker/monitor. On each trial, the two nontarget monitors showed the speaker mouthing a different sentence. Sentences were presented in noise in four test conditions: one CI, one CI plus vision, bilateral CIs, and bilateral CIs plus vision., Results: Mean percent words correct for the four test conditions were: one CI, 43%; bilateral CI, 60%; one CI plus vision, 52%; and bilateral CI plus vision, 84%. Visual information did not significantly improve performance in the single CI conditions but did improve performance in the bilateral CI conditions. The magnitude of improvement for two CIs versus one CI in the AV condition was approximately twice that for two CIs versus one CI in the auditory condition., Conclusions: Our results are consistent with previous data showing the large value of bilateral implants in a complex AV listening environment. The results indicate that the value of bilateral CIs for speech understanding is significantly underestimated in standard, auditory-only, single-speaker, test environments., Competing Interests: Dr. Dorman reports a grant from MED-EL Corporation, during the conduct of the study; and personal fees from MED-EL Corporation and Advanced Bionics, outside the submitted work. Dr. Natale reports a grant from MED-EL, during the conduct of the study. Dr. Knickerbocker reports personal fees from Arizona State University and from Center for Neurosciences, outside the submitted work., (Copyright © 2020 by the American Academy of Audiology. All rights reserved.)

Background: When cochlear implant (CI) listeners use a directional microphone or beamformer system to improve speech understanding in noise, the gain in understanding for speech presented from the front of the listener coexists with a decrease in speech understanding from the back. One way to maximize the usefulness of these systems is to keep a microphone in the omnidirectional mode in low noise and then switch to directional mode in high noise., Purpose: The purpose of this experiment was to assess the levels of speech understanding in noise allowed by a new signal processing algorithm for MED EL CIs, AutoAdaptive, which operates in the manner described previously., Research Design: Seven listeners fit with bilateral CIs were tested in a simulation of a crowded restaurant with speech presented from the front and from the back at three noise levels, 45, 55, and 65 dB SPL., Data Collection and Analysis: The listeners were seated in the middle of an array of eight loudspeakers. Sentences from the AzBio sentence lists were presented from loudspeakers at 0 or 180° azimuth. Restaurant noise at 45, 55, and 65 dB SPL was presented from all eight loudspeakers. The speech understanding scores (words correct) were subjected to a two-factor (speaker location and noise level), repeated measures, analysis of variance with posttests., Results: The analysis of variance showed a main effect for level and location and a significant interaction. Posttests showed that speech understanding scores from front and back loudspeakers did not differ significantly at the 45- and 55-dB noise levels but did differ significantly at the 65-dB noise level-with increased scores for signals from the front and decreased scores for signals from the back., Conclusions: The AutoAdaptive feature provides omnidirectional benefit at low noise levels, i.e., similar levels of speech understanding for talkers in front of, and in back of, a listener and beamformer benefit at higher noise levels, i.e., increased speech understanding for signals from in front. The automatic switching feature will be of value to the many patients who prefer not to manually switch programs on their CIs., (American Academy of Audiology.)

Objective: The objectives of this study were to assess the effectiveness of various measures of speech understanding in distinguishing performance differences between adult bimodal and bilateral cochlear implant (CI) recipients and to provide a preliminary evidence-based tool guiding clinical decisions regarding bilateral CI candidacy., Design: This study used a multiple-baseline, cross-sectional design investigating speech recognition performance for 85 experienced adult CI recipients (49 bimodal, 36 bilateral). Speech recognition was assessed in a standard clinical test environment with a single loudspeaker using the minimum speech test battery for adult CI recipients as well as with an R-SPACE 8-loudspeaker, sound-simulation system. All participants were tested in three listening conditions for each measure including each ear alone as well as in the bilateral/bimodal condition. In addition, we asked each bimodal listener to provide a yes/no answer to the question, "Do you think you need a second CI?", Results: This study yielded three primary findings: (1) there were no significant differences between bimodal and bilateral CI performance or binaural summation on clinical measures of speech recognition, (2) an adaptive speech recognition task in the R-SPACE system revealed significant differences in performance and binaural summation between bimodal and bilateral CI users, with bilateral CI users achieving significantly better performance and greater summation, and (3) the patient's answer to the question, "Do you think you need a second CI?" held high sensitivity (100% hit rate) for identifying likely bilateral CI candidates and moderately high specificity (77% correct rejection rate) for correctly identifying listeners best suited with a bimodal hearing configuration., Conclusions: Clinics cannot rely on current clinical measures of speech understanding, with a single loudspeaker, to determine bilateral CI candidacy for adult bimodal listeners nor to accurately document bilateral benefit relative to a previous bimodal hearing configuration. Speech recognition in a complex listening environment, such as R-SPACE, is a sensitive and appropriate measure for determining bilateral CI candidacy and also likely for documenting bilateral benefit relative to a previous bimodal configuration. In the absence of an available R-SPACE system, asking the patient whether or not s/he thinks s/he needs a second CI is a highly sensitive measure, which may prove clinically useful.

Objective: To evaluate outcomes in pediatric and adolescent patients with single-sided deafness (SSD) undergoing cochlear implantation., Methods: A retrospective cohort design at two tertiary level academic cochlear implant centers. The subjects included nine children ages 1.5 to 15 years-old with single-sided deafness (SSD) who had undergone cochlear implantation in the affected ear. Objective outcome measures included were speech reception testing in quiet and noise, bimodal speech reception threshold testing in noise, tinnitus suppression, and device usage., Results: Nine pediatric and adolescent patients with SSD were implanted between 2011 and 2017. The median age at implantation was 8.9 years (range, 1.5-15.1) and the children had a median duration of deafness 2.9 years (range, 0.8-9.5). There was variability in testing measures due to patient age. Median pre-operative aided word recognition scores on the affected side were <30% regardless of the testing paradigm used. Six patients had pre-operative word testing (4 CNC, median score 25%; 2 MLNT, 8% and 17%). Four patients had pre-operative sentence testing (3 AzBio, median score 44%; 1 HINT-C, 57%). Median post-implantation follow-up interval was 12.3 months (range, 3-27.6 months). Six subjects had post-operative word recognition testing (CNC median, 70%; MLNT 50%, 92%) with a median improvement of 45.5% points. Five subjects had post-operative sentence testing (AzBio, median 82%; HINT, median 76%), with a median improvement of 40.5% points. Eight patients are full time users of their device. Tinnitus and bimodal speech reception thresholds in noise were improved., Conclusion: Pediatric subjects with SSD benefit substantially from cochlear implantation. Objective speech outcome measures are improved in both quiet and noise, and bimodal speech reception thresholds in noise are greatly improved. There is a low rate of device non-use., (Copyright © 2018 Elsevier B.V. All rights reserved.)

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.

Background: Sentence understanding scores for patients with cochlear implants (CIs) when tested in quiet are relatively high. However, sentence understanding scores for patients with CIs plummet with the addition of noise., Purpose: To assess, for patients with CIs (MED-EL), (1) the value to speech understanding of two new, noise-reducing microphone settings and (2) the effect of the microphone settings on sound source localization., Research Design: Single-subject, repeated measures design. For tests of speech understanding, repeated measures on (1) number of CIs (one, two), (2) microphone type (omni, natural, adaptive beamformer), and (3) type of noise (restaurant, cocktail party). For sound source localization, repeated measures on type of signal (low-pass [LP], high-pass [HP], broadband noise)., Study Sample: Ten listeners, ranging in age from 48 to 83 yr (mean = 57 yr), participated in this prospective study., Intervention: Speech understanding was assessed in two noise environments using monaural and bilateral CIs fit with three microphone types. Sound source localization was assessed using three microphone types., Data Collection and Analysis: In Experiment 1, sentence understanding scores (in terms of percent words correct) were obtained in quiet and in noise. For each patient, noise was first added to the signal to drive performance off of the ceiling in the bilateral CI-omni microphone condition. The other conditions were then administered at that signal-to-noise ratio in quasi-random order. In Experiment 2, sound source localization accuracy was assessed for three signal types using a 13-loudspeaker array over a 180° arc. The dependent measure was root-mean-score error., Results: Both the natural and adaptive microphone settings significantly improved speech understanding in the two noise environments. The magnitude of the improvement varied between 16 and 19 percentage points for tests conducted in the restaurant environment and between 19 and 36 percentage points for tests conducted in the cocktail party environment. In the restaurant and cocktail party environments, both the natural and adaptive settings, when implemented on a single CI, allowed scores that were as good as, or better, than scores in the bilateral omni test condition. Sound source localization accuracy was unaltered by either the natural or adaptive settings for LP, HP, or wideband noise stimuli., Conclusion: The data support the use of the natural microphone setting as a default setting. The natural setting (1) provides better speech understanding in noise than the omni setting, (2) does not impair sound source localization, and (3) retains low-frequency sensitivity to signals from the rear. Moreover, bilateral CIs equipped with adaptive beamforming technology can engender speech understanding scores in noise that fall only a little short of scores for a single CI in quiet., (American Academy of Audiology)

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., (© 2018 S. Karger AG, Basel.)

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., Presentation Video: http://cred.pubs.asha.org/article.aspx?articleid=2601622.

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: To assess improvements in sound source localization and speech understanding in complex listening environments after unilateral cochlear implantation for single-sided deafness (SSD)., Study Design: Nonrandomized, open, prospective case series., Setting: Tertiary referral center., Patients: Nine subjects with a unilateral cochlear implant (CI) for SSD (SSD-CI) were tested. Reference groups for the task of sound source localization included young (n = 45) and older (n = 12) normal-hearing (NH) subjects and 27 bilateral CI (BCI) subjects., Intervention: Unilateral cochlear implantation., Main Outcome Measures: Sound source localization was tested with 13 loudspeakers in a 180 arc in front of the subject. Speech understanding was tested with the subject seated in an 8-loudspeaker sound system arrayed in a 360-degree pattern. Directionally appropriate noise, originally recorded in a restaurant, was played from each loudspeaker. Speech understanding in noise was tested using the Azbio sentence test and sound source localization quantified using root mean square error., Results: All CI subjects showed poorer-than-normal sound source localization. SSD-CI subjects showed a bimodal distribution of scores: six subjects had scores near the mean of those obtained by BCI subjects, whereas three had scores just outside the 95th percentile of NH listeners. Speech understanding improved significantly in the restaurant environment when the signal was presented to the side of the CI., Conclusion: Cochlear implantation for SSD can offer improved speech understanding in complex listening environments and improved sound source localization in both children and adults. On tasks of sound source localization, SSD-CI patients typically perform as well as BCI patients and, in some cases, achieve scores at the upper boundary of normal performance.

Many studies have documented the benefits to speech understanding when cochlear implant (CI) patients can access low-frequency acoustic information from the ear opposite the implant. In this study we assessed the role of three factors in determining the magnitude of bimodal benefit - (i) the level of CI-only performance, (ii) the magnitude of the hearing loss in the ear with low-frequency acoustic hearing and (iii) the type of test material. The patients had low-frequency PTAs (average of 125, 250 and 500 Hz) varying over a large range (<30 dB HL to >70 dB HL) in the ear contralateral to the implant. The patients were tested with (i) CNC words presented in quiet (n = 105) (ii) AzBio sentences presented in quiet (n = 102), (iii) AzBio sentences in noise at +10 dB signal-to-noise ratio (SNR) (n = 69), and (iv) AzBio sentences at +5 dB SNR (n = 64). We find maximum bimodal benefit when (i) CI scores are less than 60 percent correct, (ii) hearing loss is less than 60 dB HL in low-frequencies and (iii) the test material is sentences presented against a noise background. When these criteria are met, some bimodal patients can gain 40-60 percentage points in performance relative to performance with a CI. This article is part of a Special Issue entitled ., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The aim of this article was to study sound source localization by cochlear implant (CI) listeners with low-frequency (LF) acoustic hearing in both the operated ear and in the contralateral ear. Eight CI listeners had symmetrical LF acoustic hearing and 4 had asymmetrical LF acoustic hearing. The effects of two variables were assessed: (i) the symmetry of the LF thresholds in the two ears and (ii) the presence/absence of bilateral acoustic amplification. Stimuli consisted of low-pass, high-pass, and wideband noise bursts presented in the frontal horizontal plane. Localization accuracy was 23° of error for the symmetrical listeners and 76° of error for the asymmetrical listeners. The presence of a unilateral CI used in conjunction with bilateral LF acoustic hearing does not impair sound source localization accuracy, but amplification for acoustic hearing can be detrimental to sound source localization accuracy.

Objectives: The goal of this study was to create and validate a new set of sentence lists that could be used to evaluate the speech-perception abilities of listeners with hearing loss in cases where adult materials are inappropriate due to difficulty level or content. The authors aimed to generate a large number of sentence lists with an equivalent level of difficulty for the evaluation of performance over time and across conditions., Design: The original Pediatric AzBio sentence corpus included 450 sentences recorded from one female talker. All sentences included in the corpus were successfully repeated by kindergarten and first-grade students with normal hearing. The mean intelligibility of each sentence was estimated by processing each sentence through a cochlear implant simulation and calculating the mean percent correct score achieved by 15 normal-hearing listeners. After sorting sentences by mean percent correct scores, 320 sentences were assigned to 16 lists of equivalent difficulty. List equivalency was then validated by presenting all sentence lists, in a novel random order, to adults and children with hearing loss. A final-validation stage examined single-list comparisons from adult and pediatric listeners tested in research or clinical settings., Results: The results of the simulation study allowed for the creation of 16 lists of 20 sentences. The average intelligibility of each list ranged from 78.4 to 78.7%. List equivalency was then validated, when the results of 16 adult cochlear implant users and 9 pediatric hearing aid and cochlear implant users revealed no significant differences across lists. The binomial distribution model was used to account for the inherent variability observed in the lists. This model was also used to generate 95% confidence intervals for one and two list comparisons. A retrospective analysis of 361 instances from 78 adult cochlear implant users and 48 instances from 36 pediatric cochlear implant users revealed that the 95% confidence intervals derived from the model captured 94% of all responses (385 of 409)., Conclusions: The cochlear implant simulation was shown to be an effective method for estimating the intelligibility of individual sentences for use in the evaluation of cochlear implant users. Furthermore, the method used for constructing equivalent sentence lists and estimating the inherent variability of the materials has also been validated. Thus, the AzBio Pediatric Sentence Lists are equivalent and appropriate for the assessment of speech-understanding abilities of children with hearing loss as well as adults for whom performance on AzBio sentences is near the floor.

The aim of this project was to determine for bimodal cochlear implant (CI) patients, i.e. patients with low-frequency hearing in the ear contralateral to the implant, how speech understanding varies as a function of the difference in level between the CI signal and the acoustic signal. The data suggest that (1) acoustic signals perceived as significantly softer than a CI signal can contribute to speech understanding in the bimodal condition, (2) acoustic signals that are slightly softer than, or balanced with, a CI signal provide the largest benefit to speech understanding, and (3) acoustic signals presented at maximum comfortable loudness levels provide nearly as much benefit as signals that have been balanced with a CI signal.

The purpose of this study was to examine the availability of binaural cues for adult, bilateral cochlear implant (CI) patients, bimodal patients and hearing preservation patients using a multiple-baseline, observational study design. Speech recognition was assessed using the Bamford-Kowal-Bench Speech-in-Noise (BKB-SIN) test as well as the AzBio sentences [Spahr AJ, et al: Ear Hear 2012;33:112-117] presented in a multi-talker babble at a +5 dB signal-to-noise ratio (SNR). Test conditions included speech at 0° with noise presented at 0° (S0N0), 90° (S0N90) and 270° (S0N270). Estimates of summation, head shadow (HS), squelch and spatial release from masking (SRM) were calculated. Though nonwwe of the subject groups consistently showed access to binaural cues, the hearing preservation patients exhibited a significant correlation between summation and squelch whereas the bilateral and bimodal participants did not. That is to say, the two effects associated with binaural hearing - summation and squelch - were positively correlated only for the listeners with bilateral acoustic hearing. This finding provides evidence for the supposition that implant recipients with bilateral acoustic hearing have access to binaural cues, which should, in theory, provide greater benefit in noisy listening environments. It is likely, however, that the chosen test environment negatively affected the outcomes. Specifically, the spatially separated noise conditions directed noise toward the microphone (mic) port of the behind-the-ear (BTE) hearing aid and implant processor. Thus, it is possible that in more realistic listening environments for which the diffuse noise is not directed toward the processor/hearing aid mic, hearing preservation patients have binaural cues for improved speech understanding.

Objective: The aim of this study was to assess the benefit of having preserved acoustic hearing in the implanted ear for speech recognition in complex listening environments., Design: The present study included a within-subjects, repeated-measures design including 21 English-speaking and 17 Polish-speaking cochlear implant (CI) recipients with preserved acoustic hearing in the implanted ear. The patients were implanted with electrodes that varied in insertion depth from 10 to 31 mm. Mean preoperative low-frequency thresholds (average of 125, 250, and 500 Hz) in the implanted ear were 39.3 and 23.4 dB HL for the English- and Polish-speaking participants, respectively. In one condition, speech perception was assessed in an eight-loudspeaker environment in which the speech signals were presented from one loudspeaker and restaurant noise was presented from all loudspeakers. In another condition, the signals were presented in a simulation of a reverberant environment with a reverberation time of 0.6 sec. The response measures included speech reception thresholds (SRTs) and percent correct sentence understanding for two test conditions: CI plus low-frequency hearing in the contralateral ear (bimodal condition) and CI plus low-frequency hearing in both ears (best-aided condition). A subset of six English-speaking listeners were also assessed on measures of interaural time difference thresholds for a 250-Hz signal., Results: Small, but significant, improvements in performance (1.7-2.1 dB and 6-10 percentage points) were found for the best-aided condition versus the bimodal condition. Postoperative thresholds in the implanted ear were correlated with the degree of electric and acoustic stimulation (EAS) benefit for speech recognition in diffuse noise. There was no reliable relationship among measures of audiometric threshold in the implanted ear nor elevation in threshold after surgery and improvement in speech understanding in reverberation. There was a significant correlation between interaural time difference threshold at 250 Hz and EAS-related benefit for the adaptive speech reception threshold., Conclusions: The findings of this study suggest that (1) preserved low-frequency hearing improves speech understanding for CI recipients, (2) testing in complex listening environments, in which binaural timing cues differ for signal and noise, may best demonstrate the value of having two ears with low-frequency acoustic hearing, and (3) preservation of binaural timing cues, although poorer than observed for individuals with normal hearing, is possible after unilateral cochlear implantation with hearing preservation and is associated with EAS benefit. The results of this study demonstrate significant communicative benefit for hearing preservation in the implanted ear and provide support for the expansion of CI criteria to include individuals with low-frequency thresholds in even the normal to near-normal range.

Objectives: The authors describe the localization and speech-understanding abilities of a patient fit with bilateral cochlear implants (CIs) for whom acoustic low-frequency hearing was preserved in both cochleae., Design: Three signals were used in the localization experiments: low-pass, high-pass, and wideband noise. Speech understanding was assessed with the AzBio sentences presented in noise., Results: Localization accuracy was best in the aided, bilateral acoustic hearing condition, and was poorer in both the bilateral CI condition and when the bilateral CIs were used in addition to bilateral low-frequency hearing. Speech understanding was best when low-frequency acoustic hearing was combined with at least one CI., Conclusions: The authors found that (1) for sound source localization in patients with bilateral CIs and bilateral hearing preservation, interaural level difference cues may dominate interaural time difference cues and (2) hearing-preservation surgery can be of benefit to patients fit with bilateral CIs.

Objectives: Patients with a cochlear implant (CI) in one ear and a hearing aid in the other ear commonly achieve the highest speech-understanding scores when they have access to both electrically and acoustically stimulated information. At issue in this study was whether a measure of auditory function in the hearing aided ear would predict the benefit to speech understanding when the information from the aided ear was added to the information from the CI., Design: The subjects were 22 bimodal listeners with a CI in one ear and low-frequency acoustic hearing in the nonimplanted ear. The subjects were divided into two groups-one with mild-to-moderate low-frequency loss and one with severe-to-profound loss. Measures of auditory function included (1) audiometric thresholds at 750 Hz or lower, (2) speech-understanding scores (words in quiet and sentences in noise), and (3) spectral-modulation detection (SMD) thresholds. In the SMD task, one stimulus was a flat spectrum noise and the other was a noise with sinusoidal modulations at 1.0 peak/octave., Results: Significant correlations were found among all three measures of auditory function and the benefit to speech understanding when the acoustic and electric stimulation were combined. Benefit was significantly correlated with audiometric thresholds (r = -0.814), acoustic speech understanding (r = 0.635), and SMD thresholds (r = -0.895) in the hearing aided ear. However, only the SMD threshold was significantly correlated with benefit within the group with mild-to-moderate loss (r = -0.828) and within the group with severe-to-profound loss (r = -0.896)., Conclusions: The SMD threshold at 1 cycle/octave has the potential to provide clinicians with information relevant to the question of whether an ear with low-frequency hearing is likely to add to the intelligibility of speech provided by a CI.

Objectives: The goal of this study was to create and validate a new set of sentence lists that could be used to evaluate the speech perception abilities of hearing-impaired listeners and cochlear implant (CI) users. Our intention was to generate a large number of sentence lists with an equivalent level of difficulty for the evaluation of performance over time and across conditions., Design: The AzBio sentence corpus includes 1000 sentences recorded from two female and two male talkers. The mean intelligibility of each sentence was estimated by processing each sentence through a five-channel CI simulation and calculating the mean percent correct score achieved by 15 normal-hearing listeners. Sentences from each talker were sorted by percent correct score, and 165 sentences were selected from each talker and were then sequentially assigned to 33 lists, each containing 20 sentences (5 sentences from each talker). List equivalency was validated by presenting all lists, in random order, to 15 CI users., Results: Using sentence scores from the CI simulation study produced 33 lists of sentences with a mean score of 85% correct. The results of the validation study with CI users revealed no significant differences in percent correct scores for 29 of the 33 sentence lists. However, individual listeners demonstrated considerable variability in performance on the 29 lists. The binomial distribution model was used to account for the inherent variability observed in the lists. This model was also used to generate 95% confidence intervals for one and two list comparisons. A retrospective analysis of 172 instances where research subjects had been tested on two lists within a single condition revealed that 94% of results were accurately contained within these confidence intervals., Conclusions: The use of a five-channel CI simulation to estimate the intelligibility of individual sentences allowed for the creation of a large number of sentence lists with an equivalent level of difficulty. The results of the validation procedure with CI users found that 29 of 33 lists allowed scores that were not statistically different. However, individual listeners demonstrated considerable variability in performance across lists. This variability was accurately described by the binomial distribution model and was used to estimate the magnitude of change required to achieve statistical significance when comparing scores from one and two lists per condition. Fifteen sentence lists have been included in the AzBio Sentence Test for use in the clinical evaluation of hearing-impaired listeners and CI users. An additional eight sentence lists have been included in the Minimum Speech Test Battery to be distributed by the CI manufacturers for the evaluation of CI candidates.

The majority of recently implanted, cochlear implant patients can potentially benefit from a hearing aid in the ear contralateral to the implant. When patients combine electric and acoustic stimulation, word recognition in quiet and sentence recognition in noise increase significantly. Several studies suggest that the acoustic information that leads to the increased level of performance resides mostly in the frequency region of the voice fundamental, e.g. 125 Hz for a male voice. Recent studies suggest that this information aids speech recognition in noise by improving the recognition of lexical boundaries or word onsets. In some noise environments, patients with bilateral implants can achieve similar levels of performance as patients who combine electric and acoustic stimulation. Patients who have undergone hearing preservation surgery, and who have electric stimulation from a cochlear implant and who have low-frequency hearing in both the implanted and not-implanted ears, achieve the best performance in a high noise environment.

Objectives: Our aim was to assess, for patients with a cochlear implant in one ear and low-frequency acoustic hearing in the contralateral ear, whether reducing the overlap in frequencies conveyed in the acoustic signal and those analyzed by the cochlear implant speech processor would improve speech recognition., Design: The recognition of monosyllabic words in quiet and sentences in noise was evaluated in three listening configurations: electric stimulation alone, acoustic stimulation alone, and combined electric and acoustic stimulation. The acoustic stimuli were either unfiltered or low-pass (LP) filtered at 250, 500, or 750 Hz. The electric stimuli were either unfiltered or high-pass (HP) filtered at 250, 500, or 750 Hz. In the combined condition, the unfiltered acoustic signal was paired with the unfiltered electric signal, the 250-Hz LP acoustic signal was paired with the 250-Hz HP electric signal, the 500-Hz LP acoustic signal was paired with the 500-Hz HP electric signal, and the 750-Hz LP acoustic signal was paired with the 750-Hz HP electric signal., Results: For both acoustic and electric signals, performance increased as the bandwidth increased. The highest level of performance in the combined condition was observed in the unfiltered acoustic plus unfiltered electric condition., Conclusions: Reducing the overlap in frequency representation between acoustic and electric stimulation does not increase speech understanding scores for patients who have residual hearing in the ear contralateral to the implant. We find that acoustic information <250 Hz significantly improves performance for patients who combine electric and acoustic stimulation and accounts for the majority of the speech-perception benefit when acoustic stimulation is combined with electric stimulation.

Objectives: The primary objective of this study was to determine whether a revision and/or expansion of current audiologic cochlear implant candidacy criteria is warranted., Design: The study design was a retrospective review of postoperative speech perception performance for 22 adult cochlear implant recipients who demonstrated preoperative Consonant Nucleus Consonant word recognition scores of 30% or higher in the best-aided condition. This criterion was chosen to exceed that specified by the North American clinical trial of the Nucleus Freedom cochlear implant system., Results: The mean preoperative best-aided monosyllabic word score for the 22 patients was 41% correct. The degree of postoperative benefit for the best postoperative condition (electric only or bimodal) ranged from 10 to 68 percentage points with a mean benefit of 27 percentage points for the electric-only condition and 40 percentage points for the bimodal condition. Statistical analyses revealed highly significant differences between preoperative-aided, implant-only, and bimodal performance on Consonant Nucleus Consonant monosyllabic word recognition performance. That is, both postoperative scores--electric only and bimodal--were significantly different from one another and from the preoperative best-aided performance., Conclusions: The current results suggest that a large-scale reassessment of manufacturer and Medicare preoperative audiologic candidacy criteria for adults is warranted to allow more hearing-impaired individuals to take advantage of the benefits offered by cochlear implantation.

We have investigated the psychophysical properties of low-frequency hearing, both before and after implantation, to see if we can account for the benefit to speech understanding and melody recognition of adding acoustic stimulation to electric stimulation. In this paper, we review our work and the work of others and describe preliminary results not previously published. We show (a) that it is possible to preserve normal or near-normal nonlinear cochlear processing in the implanted ear following electric and acoustic stimulation surgery - though this is not the typical outcome; (b) that although low-frequency frequency selectivity is generally disrupted following implantation, some degree of frequency selectivity can be preserved, and (c) that neither nonlinear cochlear processing nor frequency selectivity in the acoustic hearing ear is correlated with the gain in speech understanding afforded by combined electric and acoustic stimulation. In another set of experiments, we show that the value of preserving hearing in the implanted ear is best seen in complex listening environments in which binaural cues can play a role in perception., (Copyright 2010 S. Karger AG, Basel.)

Fundamental frequency (F0) variation is one of a number of acoustic cues normal hearing listeners use for guiding lexical segmentation of degraded speech. This study examined whether F0 contour facilitates lexical segmentation by listeners fitted with cochlear implants (CIs). Lexical boundary error patterns elicited under unaltered and flattened F0 conditions were compared across three groups: listeners with conventional CI, listeners with CI and preserved low-frequency acoustic hearing, and normal hearing listeners subjected to CI simulations. Results indicate that all groups attended to syllabic stress cues to guide lexical segmentation, and that F0 contours facilitated performance for listeners with low-frequency hearing.

We compared the effectiveness of 2 surgical interventions for improving word recognition ability in a quiet environment among patients who presented with: (1) bilateral, precipitously sloping, high-frequency hearing loss; (2) relatively good auditory thresholds at and below 500 Hz, and (3) poor speech recognition. In 1 intervention (n = 25), a conventional electrode array was inserted into 1 cochlea. As a consequence, hearing was lost in the implanted ear. In the other intervention (n = 22), a Nucleus Hybrid short-electrode array was inserted 10 mm into 1 cochlea with the aim of preserving hearing in that ear. Both groups of patients had similar low-frequency hearing and speech understanding in the ear contralateral to the implant. Following surgery, both groups had significantly higher word recognition scores than before surgery. Between-group comparisons indicated that the conventional electrode array group had higher word recognition scores than the 10-mm group when stimulation was presented to the operated ear and when stimulation was presented to both ears., (Copyright 2008 S. Karger AG, Basel.)

Fifteen patients fit with a cochlear implant in one ear and a hearing aid in the other ear were presented with tests of speech and melody recognition and voice discrimination under conditions of electric (E) stimulation, acoustic (A) stimulation and combined electric and acoustic stimulation (EAS). When acoustic information was added to electrically stimulated information performance increased by 17-23 percentage points on tests of word and sentence recognition in quiet and sentence recognition in noise. On average, the EAS patients achieved higher scores on CNC words than patients fit with a unilateral cochlear implant. While the best EAS patients did not outperform the best patients fit with a unilateral cochlear implant, proportionally more EAS patients achieved very high scores on tests of speech recognition than unilateral cochlear implant patients., ((c) 2007 S. Karger AG, Basel)

Purpose: To compare the effects of conventional amplification (CA) and digital frequency compression (DFC) amplification on the speech recognition abilities of candidates for a partial-insertion cochlear implant, that is, candidates for combined electric and acoustic stimulation (EAS)., Method: The participants were 6 patients whose audiometric thresholds at 500 Hz and below were or=80 dB HL. Six tests of speech understanding were administered with CA and DFC. The Abbreviated Profile of Hearing Aid Benefit (APHAB) was also administered following use of CA and DFC., Results: Group mean scores were not statistically different in the CA and DFC conditions. However, 2 patients received substantial benefit in DFC conditions. APHAB scores suggested increased ease of communication, but also increased aversive sound quality., Conclusion: Results suggest that a relatively small proportion of individuals who meet EAS candidacy will receive substantial benefit from a DFC hearing aid and that a larger proportion will receive at least a small benefit when speech is presented against a background of noise. This benefit, however, comes at a cost-aversive sound quality.

Purpose: The authors assessed whether (a) a full-insertion cochlear implant would provide a higher level of speech understanding than bilateral low-frequency acoustic hearing, (b) contralateral acoustic hearing would add to the speech understanding provided by the implant, and (c) the level of performance achieved with electric stimulation plus contralateral acoustic hearing would be similar to performance reported in the literature for patients with a partial insertion cochlear implant., Method: Monosyllabic word recognition as well as sentence recognition in quiet and at +10 and +5 dB was assessed. Before implantation, scores were obtained in monaural and binaural conditions. Following implantation, scores were obtained in electric-only and electric-plus-contralateral acoustic conditions., Results: Postoperatively, all individuals achieved higher scores in the electric-only test conditions than they did in the best pre-implant test conditions. All individuals benefited from the addition of low-frequency information to the electric hearing., Conclusion: A full-insertion cochlear implant provides better speech understanding than bilateral, low-frequency residual hearing. The combination of an implant and contralateral acoustic hearing yields comparable performance to that of patients with a partially inserted implant and bilateral, low-frequency acoustic hearing. These data suggest that a full-insertion cochlear implant is a viable treatment option for patients with low-frequency residual hearing.

Objective: For patients with relatively good low-frequency hearing and relatively poor high-frequency hearing, who met the pre-implant criteria for combined electric and acoustic stimulation (EAS), our aims were to i) assess deficits in low-frequency auditory function, ii) to identify measures which might be sensitive to changes resulting from the insertion of an intracochlear electrode array, and iii) to quantify the relationship between measures of auditory function and performance on tasks of speech and melody recognition., Design: Measures of frequency selectivity, temporal resolution, and nonlinear cochlear function, along with measures of word, sentence, consonant, vowel, and melody recognition, were obtained from 5 normal-hearing and 17 hearing-impaired listeners. The hearing-impaired listeners had auditory thresholds at 500 Hz, ranging from 20 to 60 dB HL, and thresholds at 1 kHz, ranging from 60 to 100 dB HL., Results: Nonlinear cochlear function was either reduced or absent. Frequency selectivity at 500 Hz was significantly reduced but still present in most patients. Temporal resolution, when measured at low modulation frequencies, was normal. Speech recognition in a modulated background revealed significantly poorer performance than normal. Speech and melody recognition varied over a large range. No measure of auditory function was correlated significantly with speech recognition. However, frequency selectivity was related to melody recognition., Conclusions: (1) Patients who qualify for EAS surgery have a wide range of speech and melody recognition abilities. (2) A number of the psychophysical measures tested may prove more sensitive than the audiogram in determining the degree of damage inflicted by the intracochlear electrode array. (3) Speech recognition was not correlated with any of the measures of auditory function.

Objective: Our aim was to explore the consequences for speech understanding of leaving a gap in frequency between a region of acoustic hearing and a region stimulated electrically. Our studies were conducted with normal-hearing listeners, using an acoustic simulation of combined electric and acoustic (EAS) stimulation., Design: Simulations of EAS were created by low-pass filtering speech at 0.5 kHz (90 dB octave roll-off) and adding amplitude-modulated sine waves at higher frequencies. The gap in frequency between acoustic and simulated electric hearing was varied over the range 0.5 kHz to 3.2 kHz. Stimuli included sentences in quiet, sentences in noise, and consonants and vowels. Three experiments were conducted with sample sizes of 12 listeners., Results: Scores were highest in conditions that minimized the frequency gap between acoustic and electric stimulation. In quiet, vowels and consonant place of articulation showed the most sensitivity to the frequency gap. In noise, scores in the simulated EAS condition were higher than the sum of the scores from the acoustic-only and simulated electric-only conditions., Conclusions: Our results suggest that both deep and shallow insertions of electrodes could improve the speech understanding abilities of patients with residual hearing to 500 Hz. However, performance levels will be maximized if the gap between acoustic and electric stimulation is minimized.

Objective: The aim of this study was to assess the effects of variations in the settings for minimum stimulation levels on speech understanding for adult cochlear implant recipients using the Med El Tempo+ speech processor., Design: Fifteen patients served as listeners. The test material included sentences presented at a conversational level in noise (74 dB SPL at +10 dB signal-to-noise ratio), sentences presented at a soft level in a quiet background (54 dB SPL), consonants in "vCv" environment (74 dB SPL re: vowel peaks), and synthetic vowels in "bVt" environment (54 dB SPL re: vowel peaks). The patients' speech processors were programmed with minimum stimulation levels set to behavioral threshold, set to 10% of most comfortable loudness, and set to 0 muA., Results: The level of speech understanding achieved in the behavioral threshold condition was not significantly different from that achieved in either the 10% of most comfortable loudness or 0 muA conditions for any test material. Only 2 of the 15 patients demonstrated performance differences of greater than 10 percentage points between the 0 muA condition and the behavioral threshold condition on more than a single test., Conclusions: Our results demonstrate that there are no grievous consequences, in terms of speech understanding, for setting minimum stimulation levels below behavioral thresholds. The time savings from setting thresholds to 10% of MCL or 0 muA may be especially useful during the initial device fitting.

Objective: This study examined morphological changes in the cortical auditory evoked potential (CAEP) waveform as a function of varying stimulation rate. Stimuli were presented in a paradigm which indirectly assesses the refractory properties of the underlying neuronal generators., Methods: CAEPs were recorded in 50 normal-hearing children (3-12 years) and 10 young adults (24-26 years). A speech sound was presented in a stimulus train with sequentially decreasing inter-stimulus intervals (ISIs) of 2000, 1000, 560, and 360ms. Latencies and amplitudes of the P1, N1, and P2 components at the Cz electrode were examined as a function of stimulus rate and age., Results: Results revealed significant changes in the CAEP as a function of age and stimulation rate. At younger ages the N1-P2 component was elicited only at the slowest stimulation rates, and was more clearly apparent at successively faster stimulation rates as age increased., Conclusions: We have described a stimulus paradigm that allows examination of the development of refractoriness by highlighting the interaction between age and rate on CAEP morphology., Significance: Complex maturational patterns of CAEP components are best understood when the effects of both age and stimulus rate on the CAEP waveform are considered.

Objective: To determine if subjects who used different cochlear implant devices and who were matched on consonant-vowel-consonant (CNC) identification in quiet would show differences in performance on speech-based tests of spectral and temporal resolution, speech understanding in noise, or speech understanding at low sound levels., Design: The performance of 15 subjects fit with the CII Bionic Ear System (CII Bionic Ear behind-the-ear speech processor with the Hi-Resolution sound processing strategy; Advanced Bionics Corporation) was compared with the performance of 15 subjects fit with the Nucleus 24 electrode array and ESPrit 3G behind-the-ear speech processor with the advanced combination encoder speech coding strategy (cochlear corporation)., Subjects: Thirty adults with late-onset deafness and above-average speech perception abilities who used cochlear implants., Main Outcome Measures: Vowel recognition, consonant recognition, sentences in quiet (74, 64, and 54 dB SPL [sound pressure level]) and in noise (+10 and +5 dB SNR [signal-to-noise ratio]), voice discrimination, and melody recognition., Results: Group differences in performance were significant in 4 conditions: vowel identification, difficult sentence material at +5 dB and +10 dB SNR, and a measure that quantified performance in noise and low input levels relative to performance in quiet., Conclusions: We have identified tasks on which there are between-group differences in performance for subjects matched on CNC word scores in quiet. We suspect that the differences in performance are due to differences in signal processing. Our next goal is to uncover the signal processing attributes of the speech processors that are responsible for the differences in performance.

Electrode-pitch rankings and monaural and binaural speech perception scores were obtained from two patients fit with a Med El CIS-Link processor and Ineraid electrode array in one ear and a Clarion processor and Hi-Focus electrode array in the other ear. The results of the electrode-ranking task indicated that current from the Hi-Focus electrodes extended more apically than current from the Ineraid array, i.e., the two most apical Hi-Focus electrodes were ranked lower in pitch than the most apical Ineraid electrode. Because of this and because of the different number of active electrodes in the two arrays, it is likely that the two cochleae presented different representations of the same signal to more central stages of information processing. In spite of this, both patients achieved better scores when both implants were activated than when the implants were activated one at a time.

It is generally accepted that the fusion of two speech signals presented dichotically is affected by the relative onset time. This study investigated the hypothesis that spectral resolution might be an additional factor influencing spectral fusion when the spectral information is split and presented dichotically to the two ears. To produce speech with varying degrees of spectral resolution, speech materials embedded in +5 dB S/N speech-shaped noise were processed through 6-12 channels and synthesized as a sum of sine waves. Two different methods of splitting the spectral information were investigated. In the first method, the odd-index channels were presented to one ear and the even-index channels to the other ear. In the second method the lower frequency channels were presented to one ear and the high-frequency channels to the other ear. Results indicated that spectral resolution did affect spectral fusion, and the effect differed across speech materials, with the sentences being affected the most. Sentences, processed through six or eight channels and presented dichotically in the low-high frequency condition were not fused as accurately as when presented monaurally. Sentences presented dichotically in the odd-even frequency condition were identified more accurately than when presented in the low-high condition.

Three factors account for the high level of speech understanding in quiet enjoyed by many patients fit with cochlear implants. First, some information about speech exists in the time/amplitude envelope of speech. This information is sufficient to narrow the number of word candidates for a given signal. Second, if information from the envelope of speech is available to listeners, then only minimal information from the frequency domain is necessary for high levels of speech recognition in quiet. Third, perceiving strategies for speech are inherently flexible in terms of the mapping between signal frequencies (i.e., the locations of the formants) and phonetic identity.

The intelligibility of speech having either a single "hole" in various bands or having two "holes" in disjoint or adjacent bands in the spectrum was assessed with normal-hearing listeners. In experiment 1, the effect of spectral "holes" on vowel and consonant recognition was evaluated using speech processed through six frequency bands, and synthesized as a sum of sine waves. Results showed a modest decrease in vowel and consonant recognition performance when a single hole was introduced in the low- and high-frequency regions of the spectrum, respectively. When two spectral holes were introduced, vowel recognition was sensitive to the location of the holes, while consonant recognition remained constant around 70% correct, even when the middle- and high-frequency speech information was missing. The data from experiment 1 were used in experiment 2 to derive frequency-importance functions based on a least-squares approach. The shapes of the frequency-importance functions were found to be different for consonants and vowels in agreement with the notion that different cues are used by listeners to identify consonants and vowels. For vowels, there was unequal weighting across the various channels, while for consonants the frequency-importance function was relatively flat, suggesting that all bands contributed equally to consonant identification.

Vowels, consonants, and sentences were processed by two cochlear-implant signal-processing strategies-a fixed-channel strategy and a channel-picking strategy-and the resulting signals were presented to listeners with normal hearing for identification. At issue was the number of channels of stimulation needed in each strategy to achieve an equivalent level of speech recognition in quiet and in noise. In quiet, 8 fixed channels allowed a performance maximum for the most difficult stimulus material. A similar level of performance was reached with a 6-of-20 channel-picking strategy. In noise, 10 fixed channels allowed a performance maximum for the most difficult stimulus material. A similar level of performance was reached with a 9-of-20 strategy. Both strategies are capable of providing a very high level of speech recognition. Choosing between the two strategies may, ultimately, depend on issues that are independent of speech recognition-such as ease of device programming.

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]

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. [ABSTRACT FROM AUTHOR]

The modern cochlear implant (CI) is the most successful neural prosthesis developed to date. CIs provide hearing to the profoundly hearing impaired and allow the acquisition of spoken language in children born deaf. Results from studies enabled by the CI have provided new insights into (a) minimal representations at the periphery for speech reception, (b) brain mechanisms for decoding speech presented in quiet and in acoustically adverse conditions, (c) the developmental neuroscience of language and hearing, and (d) the mechanisms and time courses of intramodal and cross-modal plasticity. Additionally, the results have underscored the interconnectedness of brain functions and the importance of top-down processes in perception and learning. The findings are described in this review with emphasis on the developing brain and the acquisition of hearing and spoken language. [ABSTRACT FROM AUTHOR]