Speech Understanding Performance Research Articles

Resting-State Functional Connectivity Predicts Cochlear-Implant Speech Outcomes.

Cochlear implants (CIs) have revolutionized hearing restoration for individuals with severe or profound hearing loss. However, a substantial and unexplained variability persists in CI outcomes, even when considering subject-specific factors such as age and the duration of deafness. In a pioneering study, we use resting-state functional near-infrared spectroscopy to predict speech-understanding outcomes before and after CI implantation. Our hypothesis centers on resting-state functional connectivity (FC) reflecting brain plasticity post-hearing loss and implantation, specifically targeting the average clustering coefficient in resting FC networks to capture variation among CI users. Twenty-three CI candidates participated in this study. Resting-state functional near-infrared spectroscopy data were collected preimplantation and at 1 month, 3 months, and 1 year postimplantation. Speech understanding performance was assessed using consonant-nucleus-consonant words in quiet and Bamford-Kowal-Bench sentences in noise 1-year postimplantation. Resting-state FC networks were constructed using regularized partial correlation, and the average clustering coefficient was measured in the signed weighted networks as a predictive measure for implantation outcomes. Our findings demonstrate a significant correlation between the average clustering coefficient in resting-state functional networks and speech understanding outcomes, both pre- and postimplantation. This approach uses an easily deployable resting-state functional brain imaging metric to predict speech-understanding outcomes in implant recipients. The results indicate that the average clustering coefficient, both pre- and postimplantation, correlates with speech understanding outcomes.

Selective attention decoding in bimodal cochlear implant users.

The growing group of cochlear implant (CI) users includes subjects with preserved acoustic hearing on the opposite side to the CI. The use of both listening sides results in improved speech perception in comparison to listening with one side alone. However, large variability in the measured benefit is observed. It is possible that this variability is associated with the integration of speech across electric and acoustic stimulation modalities. However, there is a lack of established methods to assess speech integration between electric and acoustic stimulation and consequently to adequately program the devices. Moreover, existing methods do not provide information about the underlying physiological mechanisms of this integration or are based on simple stimuli that are difficult to relate to speech integration. Electroencephalography (EEG) to continuous speech is promising as an objective measure of speech perception, however, its application in CIs is challenging because it is influenced by the electrical artifact introduced by these devices. For this reason, the main goal of this work is to investigate a possible electrophysiological measure of speech integration between electric and acoustic stimulation in bimodal CI users. For this purpose, a selective attention decoding paradigm has been designed and validated in bimodal CI users. The current study included behavioral and electrophysiological measures. The behavioral measure consisted of a speech understanding test, where subjects repeated words to a target speaker in the presence of a competing voice listening with the CI side (CIS) only, with the acoustic side (AS) only or with both listening sides (CIS+AS). Electrophysiological measures included cortical auditory evoked potentials (CAEPs) and selective attention decoding through EEG. CAEPs were recorded to broadband stimuli to confirm the feasibility to record cortical responses with CIS only, AS only, and CIS+AS listening modes. In the selective attention decoding paradigm a co-located target and a competing speech stream were presented to the subjects using the three listening modes (CIS only, AS only, and CIS+AS). The main hypothesis of the current study is that selective attention can be decoded in CI users despite the presence of CI electrical artifact. If selective attention decoding improves combining electric and acoustic stimulation with respect to electric stimulation alone, the hypothesis can be confirmed. No significant difference in behavioral speech understanding performance when listening with CIS+AS and AS only was found, mainly due to the ceiling effect observed with these two listening modes. The main finding of the current study is the possibility to decode selective attention in CI users even if continuous artifact is present. Moreover, an amplitude reduction of the forward transfer response function (TRF) of selective attention decoding was observed when listening with CIS+AS compared to AS only. Further studies to validate selective attention decoding as an electrophysiological measure of electric acoustic speech integration are required.

Predicting speech intelligibility from a selective attention decoding paradigm in cochlear implant users

Objectives. Electroencephalography (EEG) can be used to decode selective attention in cochlear implant (CI) users. This work investigates if selective attention to an attended speech source in the presence of a concurrent speech source can predict speech understanding in CI users. Approach. CI users were instructed to attend to one out of two speech streams while EEG was recorded. Both speech streams were presented to the same ear and at different signal to interference ratios (SIRs). Speech envelope reconstruction of the to-be-attended speech from EEG was obtained by training decoders using regularized least squares. The correlation coefficient between the reconstructed and the attended ( or the unattended speech stream at each SIR was computed. Additionally, we computed the difference correlation coefficient at the same and opposite SIR (. compares the attended and unattended correlation coefficient to speech sources presented at different presentation levels depending on SIR. In contrast, compares the attended and unattended correlation coefficients to speech sources presented at the same presentation level irrespective of SIR. Main results. Selective attention decoding in CI users is possible even if both speech streams are presented monaurally. A significant effect of SIR on , and ρ DiffOpp, but not on , was observed. Finally, the results show a significant correlation between speech understanding performance and as well as with across subjects. Moreover, ρ DiffOpp which is less affected by the CI artifact, also demonstrated a significant correlation with speech understanding. Significance. Selective attention decoding in CI users is possible, however care needs to be taken with the CI artifact and the speech material used to train the decoders. These results are important for future development of objective speech understanding measures for CI users.

Assessing the relationship between neural health measures and speech performance with simultaneous electric stimulation in cochlear implant listeners.

ObjectivesThe relationship between electrode-nerve interface (ENI) estimates and inter-subject differences in speech performance with sequential and simultaneous channel stimulation in adult cochlear implant listeners were explored. We investigated the hypothesis that individuals with good ENIs would perform better with simultaneous compared to sequential channel stimulation speech processing strategies than those estimated to have poor ENIs.MethodsFourteen postlingually deaf implanted cochlear implant users participated in the study. Speech understanding was assessed with a sentence test at signal-to-noise ratios that resulted in 50% performance for each user with the baseline strategy F120 Sequential. Two simultaneous stimulation strategies with either two (Paired) or three sets of virtual channels (Triplet) were tested at the same signal-to-noise ratio. ENI measures were estimated through: (I) voltage spread with electrical field imaging, (II) behavioral detection thresholds with focused stimulation, and (III) slope (IPG slope effect) and 50%-point differences (dB offset effect) of amplitude growth functions from electrically evoked compound action potentials with two interphase gaps.ResultsA significant effect of strategy on speech understanding performance was found, with Triplets showing a trend towards worse speech understanding performance than sequential stimulation. Focused thresholds correlated positively with the difference required to reach most comfortable level (MCL) between Sequential and Triplet strategies, an indirect measure of channel interaction. A significant offset effect (difference in dB between 50%-point for higher eCAP growth function slopes with two IPGs) was observed. No significant correlation was observed between the slopes for the two IPGs tested. None of the measures used in this study correlated with the differences in speech understanding scores between strategies.ConclusionsThe ENI measure based on behavioral focused thresholds could explain some of the difference in MCLs, but none of the ENI measures could explain the decrease in speech understanding with increasing pairs of simultaneously stimulated electrodes in processing strategies.

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

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

The effects of behind-the-ear and off-the-ear sound processors on speech understanding performance in cochlear implant users

ObjectiveThe first aim of this study was to compare speech understanding performance in adult cochlear implant users using behind-the-ear and off-the-ear sound processors in quiet and noise. Second, the impact of sound processor microphone location on speech understanding performance was compared. MethodsParticipants were tested with both types of sound processors in the free field with warble tones, and speech discrimination scores in quiet were obtained. Turkish Matrix Test was used to measure speech understanding in noise with five different loudspeaker settings. Twenty-seven participants of cochlear implants between 16 and 67 years-of-age using behind-the-ear or off-the-ear sound processors were included in the study. The results obtained with two types of sound processors were compared. ResultsAided free field thresholds were significantly better for the behind-the-ear vs. off-the-ear sound processor. The mean difference was 3.3 dB HL. There was no significant difference in speech discrimination scores in quite between the two processors (p > 0.05). Statistically significant differences were not seen for speech intelligibility in five spatial settings in the Turkish Matrix Test (p > 0.05). ConclusionAlthough both types of sound processors had different microphone locations, the outcomes were found to be consistent with previous results in adult users off-the-ear sound processors, demonstrating equivalent speech understanding in quiet and noise.

Hearing impairment is associated with enhanced neural tracking of the speech envelope

Elevated hearing thresholds in hearing impaired adults are usually compensated by providing amplification through a hearing aid. In spite of restoring hearing sensitivity, difficulties with understanding speech in noisy environments often remain. One main reason is that sensorineural hearing loss not only causes loss of audibility but also other deficits, including peripheral distortion but also central temporal processing deficits. To investigate the neural consequences of hearing impairment in the brain underlying speech-in-noise difficulties, we compared EEG responses to natural speech of 14 hearing impaired adults with those of 14 age-matched normal-hearing adults. We measured neural envelope tracking to sentences and a story masked by different levels of a stationary noise or competing talker. Despite their sensorineural hearing loss, hearing impaired adults showed higher neural envelope tracking of the target than the competing talker, similar to their normal-hearing peers. Furthermore, hearing impairment was related to an additional increase in neural envelope tracking of the target talker, suggesting that hearing impaired adults may have an enhanced sensitivity to envelope modulations or require a larger differential neural tracking of target versus competing talker to segregate speech from noise. Lastly, both normal-hearing and hearing impaired participants showed an increase in neural envelope tracking with increasing speech understanding. Hence, our results open avenues towards new clinical applications, such as neuro-steered prostheses as well as objective and automatic measurements of speech understanding performance.

Effect of Stimulation Rate on Speech Understanding in Older Cochlear-Implant Users.

Cochlear implants (CIs) are considered a safe and effective intervention for more severe degrees of hearing loss in adults of all ages. Although older CI users ≥65 years of age can obtain large benefits in speech understanding from a CI, there is a growing body of literature suggesting that older CI users may not perform as well as younger CI users. One reason for this potential age-related limitation could be that default CI stimulation settings are not optimal for older CI users. The goal of this study was to determine whether improvements in speech understanding were possible when CI users were programmed with nondefault stimulation rates and to determine whether lower-than-default stimulation rates improved older CI users' speech understanding. Sentence recognition was measured acutely using different stimulation rates in 37 CI users ranging in age from 22 to 87 years. Maps were created using rates of 500, 720, 900, and 1200 pulses per second (pps) for each subject. An additional map using a rate higher than 1200 pps was also created for individuals who used a higher rate in their clinical processors. Thus, the clinical rate of each subject was also tested, including non-default rates above 1200 pps for Cochlear users and higher rates consistent with the manufacturer defaults for subjects implanted with Advanced Bionics and Med-El devices. Speech understanding performance was evaluated at each stimulation rate using AzBio and Perceptually Robust English Sentence Test Open-set (PRESTO) sentence materials tested in quiet and in noise. For Cochlear-brand users, speech understanding performance using non-default rates was slightly poorer when compared with the default rate (900 pps). However, this effect was offset somewhat by age, in which older subjects were able to maintain comparable performance using a 500-pps map compared with the default rate map when listening to the more difficult PRESTO sentence material. Advanced Bionics and Med-El users showed modest improvements in their overall performance using 720 pps compared with the default rate (>1200 pps). On the individual-subject level, 10 subjects (11 ears) showed a significant effect of stimulation rate, with 8 of those ears performing best with a lower-than-default rate. Results suggest that default stimulation rates are likely sufficient for many CI users, but some CI users at any age can benefit from a lower-than-default rate. Future work that provides experience with novel rates in everyday life has the potential to identify more individuals whose performance could be improved with changes to stimulation rate.

Age-Related Temporal Processing Deficits in Word Segments in Adult Cochlear-Implant Users.

Aging may limit speech understanding outcomes in cochlear-implant (CI) users. Here, we examined age-related declines in auditory temporal processing as a potential mechanism that underlies speech understanding deficits associated with aging in CI users. Auditory temporal processing was assessed with a categorization task for the words dish and ditch (i.e., identify each token as the word dish or ditch) on a continuum of speech tokens with varying silence duration (0 to 60 ms) prior to the final fricative. In Experiments 1 and 2, younger CI (YCI), middle-aged CI (MCI), and older CI (OCI) users participated in the categorization task across a range of presentation levels (25 to 85 dB). Relative to YCI, OCI required longer silence durations to identify ditch and exhibited reduced ability to distinguish the words dish and ditch (shallower slopes in the categorization function). Critically, we observed age-related performance differences only at higher presentation levels. This contrasted with findings from normal-hearing listeners in Experiment 3 that demonstrated age-related performance differences independent of presentation level. In summary, aging in CI users appears to degrade the ability to utilize brief temporal cues in word identification, particularly at high levels. Age-specific CI programming may potentially improve clinical outcomes for speech understanding performance by older CI listeners.

Improving Speech Recognition in Bilateral Cochlear Implant Users by Listening With the Better Ear.

For patients with bilateral cochlear implants (BiCIs), understanding a target talker in a noisy situation can be difficult. Current efforts for improving speech-in-noise understanding have focused on improving signal-to-noise ratio by using multiple microphones or signal processing, with only moderate improvements in speech understanding performance. However, BiCI users typically report having a better ear for listening which can lead to an asymmetry in speech unmasking performance. This work proposes a novel listening strategy for improving speech-in-noise understanding by combining (a) a priori knowledge of a better ear and having a BiCI user selectively attend to a target talker in that ear with (b) signal processing that delivers the target talker to the better ear and the noisy background to the opposite ear. This strategy is different from traditional noise reduction strategies because it maintains situational awareness (background sounds are delivered to the ear contralateral to the better ear) while improving speech understanding. Speech recognition performance was evaluated with and without the better ear strategy in a speech-in-noise listening test using a virtual auditory space created from individualized head-related transfer functions. Listeners showed an average improvement of 4.4 dB signal-to-noise ratio in their speech reception threshold when using the better ear strategy with no listener showing a decrement in performance. This implies that the strategy has the potential to boost speech-in-noise recognition in BiCI users and may be useful in other hearing assistance devices such as hearing aids.

Effect of auditory temporal processing training on behavioral and electrophysiological functions in central presbycusis

ObjectiveAge-related changes in the central auditory system, particularly auditory temporal processing abilities, were considered among most important factors affecting speech understanding performance in older adults. Once these factors are identified, clinical management procedures could be developed for prevention and treatment. The aim of this study was to determine the effects of short-term auditory training on the behavioral and electrophysiological measurements of auditory function in individuals with age-related temporal processing deficit.Participants and methodsA prospective study of 20 individuals aged 60–67 years with either normal or bilateral symmetric high-frequency hearing loss was conducted. Evaluations of auditory temporal processing using behavioral tests (Pitch Discrimination Test, Pitch Pattern Sequence Test, Auditory Fusion Test-Revised, and Time Compressed Speech Test), P300 potential, and the administration of ‘Amsterdam inventory for auditory disability and handicap’ were performed before and after short-term auditory training.ResultsAll participants demonstrated poor pretraining Pitch Pattern Sequence Test results which were significantly improved after remediation. All patients showed normal pretraining performance on Pitch Discrimination Test, Auditory Fusion Test-Revised, and Time Compressed Speech Test tests. There was a statistically significant increase in P300 amplitude and shortening in latency after remediation.ConclusionShort-term auditory training in older adults with auditory temporal processing deficit led to improvements in temporal sequencing skills and communication in noisy environments. P300 potential has been proved to be an objective indicator of neurophysiologic changes in the central auditory system resulting from auditory experience.RecommendationShort-term auditory training is an efficient rehabilitative tool for elderly people with auditory temporal processing deficit. However, maintenance of treatment effects over time should be evaluated.

Age-Related Differences in the Processing of Temporal Envelope and Spectral Cues in a Speech Segment.

As people age, they experience reduced temporal processing abilities. This results in poorer ability to understand speech, particularly for degraded input signals. Cochlear implants (CIs) convey speech information via the temporal envelopes of a spectrally degraded input signal. Because there is an increasing number of older CI users, there is a need to understand how temporal processing changes with age. Therefore, the goal of this study was to quantify age-related reduction in temporal processing abilities when attempting to discriminate words based on temporal envelope information from spectrally degraded signals. Younger normal-hearing (YNH) and older normal-hearing (ONH) participants were presented a continuum of speech tokens that varied in silence duration between phonemes (0 to 60 ms in 10-ms steps), and were asked to identify whether the stimulus was perceived more as the word "dish" or "ditch." Stimuli were vocoded using tonal carriers. The number of channels (1, 2, 4, 8, 16, and unprocessed) and temporal envelope low-pass filter cutoff frequency (50 and 400 Hz) were systematically varied. For the unprocessed conditions, the YNH participants perceived the word ditch for smaller silence durations than the ONH participants, indicating that aging affects temporal processing abilities. There was no difference in performance between the unprocessed and 16-channel, 400-Hz vocoded stimuli. Decreasing the number of spectral channels caused decreased ability to distinguish dish and ditch. Decreasing the envelope cutoff frequency also caused decreased ability to distinguish dish and ditch. The overall pattern of results revealed that reductions in spectral and temporal information had a relatively larger effect on the ONH participants compared with the YNH participants. Aging reduces the ability to utilize brief temporal cues in speech segments. Reducing spectral information-as occurs in a channel vocoder and in CI speech processing strategies-forces participants to use temporal envelope information; however, older participants are less capable of utilizing this information. These results suggest that providing as much spectral and temporal speech information as possible would benefit older CI users relatively more than younger CI users. In addition, the present findings help set expectations of clinical outcomes for speech understanding performance by adult CI users as a function of age.

The effects of early auditory-based intervention on adult bilateral cochlear implant outcomes

Objectives: The goal of this exploratory study was to determine the types of improvement that sequentially implanted auditory-verbal and auditory-oral adults with prelingual and childhood hearing loss received in bilateral listening conditions, compared to their best unilateral listening condition.Methods: Five auditory-verbal adults and five auditory-oral adults were recruited for this study. Participants were seated in the center of a 6-loudspeaker array. BKB-SIN sentences were presented from 0° azimuth, while multi-talker babble was presented from various loudspeakers. BKB-SIN scores in bilateral and the best unilateral listening conditions were compared to determine the amount of improvement gained.Results: As a group, the participants had improved speech understanding scores in the bilateral listening condition. Although not statistically significant, the auditory-verbal group tended to have greater speech understanding with greater levels of competing background noise, compared to the auditory-oral participants.Discussion: Bilateral cochlear implantation provides individuals with prelingual and childhood hearing loss with improved speech understanding in noise. A higher emphasis on auditory development during the critical language development years may add to increased speech understanding in adulthood. However, other demographic factors such as age or device characteristics must also be considered.Conclusion: Although both auditory-verbal and auditory-oral approaches emphasize spoken language development, they emphasize auditory development to different degrees. This may affect cochlear implant (CI) outcomes. Further consideration should be made in future auditory research to determine whether these differences contribute to performance outcomes. Additional investigation with a larger participant pool, controlled for effects of age and CI devices and processing strategies, would be necessary to determine whether language learning approaches are associated with different levels of speech understanding performance.

Smartphone-based noise adaptive speech enhancement for hearing aid applications.

It is well established that the presence of environmental noises has a negative impact on the performance of hearing aid devices. This paper addresses a noise adaptive speech enhancement solution for the purpose of improving the performance of hearing aid devices in noisy environments. Depending on three noise types of babble, machinery, and driving car, the parameters of a recently developed speech enhancement algorithm are appropriately adjusted to gain improved speech understanding performance in noisy environments. This solution is implemented on smartphone platforms as an app and interfaced with a hearing aid device. A clinical testing protocol is devised to evaluate the performance of the app in participants with normal hearing and hearing impairments. The clinical testing results have indicated that statistically significant improvement in speech understanding is gained between the unprocessed and processed conditions using the developed noise adaptive speech enhancement solution.

Method of Speech Stimulus Presentation Impacts Pediatric Speech Recognition

To characterize the potential differences in speech understanding performance on word and sentence tests assessed using live voice and recorded speech measures for pediatric cochlear implant (CI) recipients. This clinical study used a combination of retrospective and prospective study designs exploring within-subject performance for recorded versus monitored-live-voice presentation methods on pediatric word and sentence measures. Word and/or sentence recognition was obtained for 29 pediatric CI recipients using both recorded stimuli and monitored-live-voice (MLV) within a single-test session with a single experimenter for each session. The difference score was calculated for word and sentence measures allowing a comparison across conditions. Ambulatory. Pediatric patients aged 4 to 17 years. Cochlear implants. Speech recognition testing. There was a significant difference between recorded and MLV speech understanding with mean recorded word scores being 13-percentage points lower than those obtained via MLV. The results of this project suggest that the use of MLV for the assessment of speech perception in the pediatric Audiology clinic may overinflate children's performance and thereby runs the risk of failing to identify poorer or at-risk performance.

Pitch Discrimination: An Independent Factor in Cochlear Implant Performance Outcomes.

Objective:To assess differences in pitch-ranking ability across a range of speech understanding performance levels and as a function of electrode position.Study Design:An observational study of a cross-section of cochlear implantees.Setting:Tertiary referral center for cochlear implantation.Patients:A total of 22 patients were recruited. All three manufacturers’ devices were included (MED-EL, Innsbruck, Austria, n = 10; Advanced Bionics, California, USA, n = 8; and Cochlear, Sydney, Australia, n = 4) and all patients were long-term users (more than 18 months). Twelve of these were poor performers (scores on BKB sentence lists <60%) and 10 were excellent performers (BKB >90%).Intervention:After measurement of threshold and comfort levels, and loudness balancing across the array, all patients underwent thorough pitch-ranking assessments at 80% of comfort levels.Main Outcome Measure:Ability to discriminate pitch across the electrode array, measured by consistency in discrimination of adjacent pairs of electrodes, as well as an assessment of the pitch order across the array using the midpoint comparison task.Results:Within the poor performing group there was wide variability in ability to pitch rank, from no errors, to a complete inability to reliably and consistently differentiate pitch change across the electrode array. Good performers were overall significantly more accurate at pitch ranking (p = 0.026). Consistent pitch ranking was found to be a significant independent predictor of BKB score, even after adjusting for age. Users of the MED-EL implant experienced significantly more pitch confusions at the apex than at more basal parts of the electrode array.Conclusions:Many cochlear implant users struggle to discriminate pitch effectively. Accurate pitch ranking appears to be an independent predictor of overall outcome. Future work will concentrate on manipulating maps based upon pitch discrimination findings in an attempt to improve speech understanding.

Age-related hearing loss, noise-induced hearing loss, and speech-understanding performance

Karl Kryter was keenly interested in the effects of noise on hearing, the interaction of age-related hearing loss (ARHL) with noise-induced hearing loss (NIHL), and, ultimately, the consequences of both on an individual’s ability to understand speech in quiet and in noise. This review will touch on each of these topics and the interrelationships among them. The focus of this presentation will be on discussion of factors impacting the speech-understanding performance of older adults, with parallels drawn for NIHL where possible. Factors considered will include those represented by a variety of peripheral-auditory, central-auditory, and cognitive measures. Interactions among these factors will also be reviewed.

Speech-in-Noise and Subjective Benefit With Active Middle Ear Implant Omnidirectional and Directional Microphones

1) To evaluate speech understanding in noise by comparing signal-to-noise ratios for 50% correct word understanding (SNR50) using an omnidirectional and a directional microphone audio processor (AP) in 4 different noise conditions. 2) To compare subjective speech understanding abilities, spatial hearing abilities, and qualitative hearing performance with the 2 processors. A prospective, single-subjects repeated-measures study design was used to compare speech understanding performance with the 2 APs acutely and after 6 weeks' acclimatization time. Tertiary referral center. Thirteen experienced unilateral German-speaking active middle ear implant users with either mixed or conductive hearing loss were enrolled. Directional audio processor. SNR50 obtained from 4 different noise conditions. SNR50s with the directional AP were lower (better) than with the omnidirectional AP in all noise conditions, although there were no changes in aided PTA thresholds. In acute testing, the mean SNR50 showed a significant directional advantage (DA) for the directional AP in the S0N0 condition of 1.3 dB, in S0NVSB 2.3 dB, in S0Ncont 3.1 dB, and in S0N180 4.5 dB. As expected, the largest DA was found in the S0N180 condition. No DA was expected in the S0N0 condition but was present. After 6 weeks of acclimatization time, no significant change from the acute testing was found, suggesting that patients experienced improved performance with the directional AP, even without acclimatization time. There was no significant change in subjective questionnaire outcomes. The directional AP yields immediately improved speech understanding in noise.

Speech Understanding Performance of Cochlear Implant Subjects Using Time–Frequency Masking-Based Noise Reduction

Cochlear implant (CI) recipients report severe degradation of speech understanding under noisy conditions. Most CI recipients typically can require about 10-25 dB higher signal-to-noise ratio than normal hearing (NH) listeners in order to achieve similar speech understanding performance. In recent years, significant emphasis has been put on binaural algorithms, which not only make use of the head shadow effect, but also have two or more microphone signals at their disposal to generate binaural inputs. Most of the CI recipients today are unilaterally implanted but they can still benefit from the binaural processing utilizing a contralateral microphone. The phase error filtering (PEF) algorithm tries to minimize the phase error variance utilizing a time-frequency mask for noise reduction. Potential improvement in speech intelligibility offered by the algorithm is evaluated with four different kinds of mask functions. The study reveals that the PEF algorithm which uses a contralateral microphone but unilateral presentation provides considerable improvement in intelligibility for both NH and CI subjects. Further, preference rating test suggests that CI subjects can tolerate higher levels of distortions than NH subjects, and therefore, more aggressive noise reduction for CI recipients is possible.

Evaluation of noise reduction technologies in a contemporary cochlear implant system

Evaluation of noise reduction technologies in a contemporary cochlear implant system