Speech Processing Strategies Research Articles

Examining the psychometric properties of the Columbia Speech Quality Instrument in cochlear implant users

ObjectiveAlthough speech recognition among cochlear implant (CI) users improved over the past few decades, many still report poor speech quality. Currently, there is no validated tool to measure speech quality. The objective was to examine whether a previously validated speech quality tool is applicable in the CI population using psychometric analysis.DesignCross-sectional psychometric analysis of the Columbia Speech Quality Instrument (CSQI; previously validated in normal-hearing individuals; consists of 2 original and 7 manipulated speech clips designed to accentuate selected speech characteristics) was performed in adult English-speaking CI recipients (N = 36). Subjects rated each clip using a visual analog scale (VAS) on 14 characteristics: cartoonish/not-cartoonish, clear/unclear, like/dislike, breathy/not-breathy, smooth/rough, echo-y/not-echo-y, tinny/bassy, soothing/not-soothing, natural/unnatural, mechanical/not-mechanical, hoarse/smooth, pleasant/unpleasant, male/female, and speech-like/not-speech-like. Main outcome measures included validity, reliability, and factor structure.ResultsContent validity was previously confirmed during instrument design. Construct validity by item-item correlation analysis demonstrated correlation of 12/14 items with ≥1 other retained item (r ≥ 0.35, Spearman). Reliability was confirmed by internal consistency; factor analysis using two subsets selected by Scree plot and factor loading ≥0.4 demonstrated Cronbach alpha coefficients of 0.89 and 0.74 for factors 1 and 2, respectively. Tinny/bassy and male/female were the only characteristics that did not pass construct validity or internal consistency.ConclusionsThe CSQI has strong psychometric properties in the CI population; however, our findings support removal of tinny/bass and male/female characteristics from the final instrument prior to implementation in the CI population. The CSQI can be utilized in cochlear implantees to investigate effects of changes in speech processing strategies and postoperative outcomes with different devices.

The Effect of Noise on the Utilization of Fundamental Frequency and Formants for Voice Discrimination in Children and Adults

The ability to discriminate between talkers based on their fundamental (F0) and formant frequencies can facilitate speech comprehension in multi-talker environments. To date, voice discrimination (VD) of children and adults has only been tested in quiet conditions. This study examines the effect of speech-shaped noise on the use of F0 only, formants only, and the combined F0 + formant cues for VD. A total of 24 adults (18–35 years) and 16 children (7–10 years) underwent VD threshold assessments in quiet and noisy environments with the tested cues. Thresholds were obtained using a three-interval, three-alternative, two-down, one-up adaptive procedure. The results demonstrated that noise negatively impacted the utilization of formants for VD. Consequently, F0 became the lead cue for VD for the adults in noisy environments, whereas the formants were the more accessible cue for VD in quiet environments. For children, however, both cues were poorly utilized in noisy environments. The finding that robust cues such as formants are not readily available for VD in noisy conditions has significant clinical implications. Specifically, the reliance on F0 in noisy environments highlights the difficulties that children encounter in multi-talker environments due to their poor F0 discrimination and emphasizes the importance of maintaining F0 cues in speech-processing strategies tailored for hearing devices.

Familiar and unfamiliar speaker recognition assessment and system emulation for cochlear implant users.

In the area of speech processing, human speaker identification under naturalistic environments is a challenging task, especially for hearing-impaired individuals with cochlear implants (CIs) or hearing aids (HAs). Motivated by the fact that electrodograms reflect direct CI stimulation of input audio, this study proposes a speaker identification (ID) investigation using two-dimensional electrodograms constructed from the responses of a CI auditory system to emulate CI speaker ID capabilities. Features are extracted from electrodograms through an identity vector (i-vector) framework to train and generate identity models for each speaker using a Gaussian mixture model-universal background model followed by probabilistic linear discriminant analysis. To validate the proposed system, perceptual speaker ID for 20 normal hearing (NH) and seven CI listeners was evaluated with a total of 41 different speakers and compared with the scores from the proposed system. A one-way analysis of variance showed that the proposed system can reliably predict the speaker ID capability of CI (F[1,10] = 0.18, p = 0.68) and NH (F[1,20] = 0, p = 0.98) listeners in naturalistic environments. The impact of speaker familiarity is also addressed, and the results show a reduced performance for speaker recognition by CI subjects using their CI processor, highlighting limitations of current speech processing strategies used in CIs/HAs.

Pre-attentive fundamental frequency processing in Mandarin-speaking children with cochlear implants as revealed by the peak latency of positive mismatch response.

Fundamental frequency (F0) serves as the primary acoustic cue for Mandarin tone perception. Recent behavioral studies suggest that F0 information may be differently processed between Mandarin-speaking normal-hearing (NH) children and children with cochlear implants (CIs), which may partially explain the unsatisfactory outcome of lexical tone recognition using CIs with tonal language-oriented speech processing strategies. The aim of the current study was to provide neural evidence of F0 processing in Mandarin-speaking kindergarten-aged children with CIs compared with NH children. Positive mismatch responses (p-MMRs) to the change of the two acoustic dimensions of F0 (F0 contour and F0 level) in Mandarin-speaking kindergarten-aged children with CIs (n = 19) and their age-matched NH peers (n = 21). The two groups of children did not show any significant difference on the mean amplitude of p-MMR to either F0 contour or F0 level change. While the CI group exhibited a significantly shorter peak latency of p-MMR to F0 contour change than to F0 level change, an opposite pattern was observed in the NH group. This study revealed a higher sensitivity to F0 contour change than to F0 level change in children with CIs, which was different from that in NH children. The neural evidence of discrepant F0 processing between children with CIs and NH children in this study was consistent with the previously reported behavioral findings and may serve as a reference for the development and improvement of tonal language-oriented speech processing strategies.

Analysis of outcomes for communication mode in cochlear implant in prelingually deafened adults

ObjectiveRecent studies have suggested that speech perception outcomes after cochlear implantation (CI) in prelingually deafened adults have improved with advances in CI technology and speech processing strategies. However, the outcomes vary from case to case. Communication mode has been reported in many studies as the factor that related to the post CI outcomes. This study aimed at investigating the post CI outcomes and the progress during 2 years for each communication mode. Material and MethodsThe subjects were 17 prelingually deafened adults undergoing CI at our hospital between April 2013 and March 2019. We investigated preoperative factors affecting post CI outcomes. Also we analyzed post CI outcomes for each communication mode and compared preoperative factors for each communication mode. ResultsCommunication mode and preoperative discrimination score were the factor affecting on postoperative discrimination score. The speech perception score after CI improved significantly in the oral and lip-reading group and total communication group. The speech perception scores in postlingually deafened adults improved significantly during the first six months and became to plateau after CI. On the other hand, the scores of prelingually deafened adults tended to improve gradually after six months postoperatively. Furthermore, the degree of improvement and progress differed by each communication mode. ConclusionThe communication mode is important factors in predicting outcomes in prelingually deafened adults after CI. Long-term auditory training is important for prelingually deafened adults who use visual information as their preoperative method of communication.

Differential weighting of temporal envelope cues from the low-frequency region for Mandarin sentence recognition in noise

BackgroundTemporal envelope cues are conveyed by cochlear implants (CIs) to hearing loss patients to restore hearing. Although CIs could enable users to communicate in clear listening environments, noisy environments still pose a problem. To improve speech-processing strategies used in Chinese CIs, we explored the relative contributions made by the temporal envelope in various frequency regions, as relevant to Mandarin sentence recognition in noise.MethodsOriginal speech material from the Mandarin version of the Hearing in Noise Test (MHINT) was mixed with speech-shaped noise (SSN), sinusoidally amplitude-modulated speech-shaped noise (SAM SSN), and sinusoidally amplitude-modulated (SAM) white noise (4 Hz) at a + 5 dB signal-to-noise ratio, respectively. Envelope information of the noise-corrupted speech material was extracted from 30 contiguous bands that were allocated to five frequency regions. The intelligibility of the noise-corrupted speech material (temporal cues from one or two regions were removed) was measured to estimate the relative weights of temporal envelope cues from the five frequency regions.ResultsIn SSN, the mean weights of Regions 1–5 were 0.34, 0.19, 0.20, 0.16, and 0.11, respectively; in SAM SSN, the mean weights of Regions 1–5 were 0.34, 0.17, 0.24, 0.14, and 0.11, respectively; and in SAM white noise, the mean weights of Regions 1–5 were 0.46, 0.24, 0.22, 0.06, and 0.02, respectively.ConclusionsThe results suggest that the temporal envelope in the low-frequency region transmits the greatest amount of information in terms of Mandarin sentence recognition for three types of noise, which differed from the perception strategy employed in clear listening environments.

Modulation Depth Discrimination by Cochlear Implant Users

Cochlear implants (CIs) convey the amplitude envelope of speech by modulating high-rate pulse trains. However, not all of the envelope may be necessary to perceive amplitude modulations (AMs); the effective envelope depth may be limited by forward and backward masking from the envelope peaks. Three experiments used modulated pulse trains to measure which portions of the envelope can be effectively processed by CI users as a function of AM frequency. Experiment 1 used a three-interval forced-choice task to test the ability of CI users to discriminate less-modulated pulse trains from a fully modulated standard, without controlling for loudness. The stimuli in experiment 2 were identical, but a two-interval task was used in which participants were required to choose the less-modulated interval, ignoring loudness. Catch trials, in which judgements based on level or modulation depth would give opposing answers, were included. Experiment 3 employed novel stimuli whose modulation envelope could be modified below a variable point in the dynamic range, without changing the loudness of the stimulus. Overall, results showed that substantial portions of the envelope are not accurately encoded by CI users. In experiment 1, where loudness cues were available, participants on average were insensitive to changes in the bottom 30% of their dynamic range. In experiment 2, where loudness was controlled, participants appeared insensitive to changes in the bottom 50% of the dynamic range. In experiment 3, participants were insensitive to changes in the bottom 80% of the dynamic range. We discuss potential reasons for this insensitivity and implications for CI speech-processing strategies.

The Relationship Between Impedance, Programming and Word Recognition in a Large Clinical Dataset of Cochlear Implant Recipients.

Cochlear implant programming typically involves measuring electrode impedance, selecting a speech processing strategy and fitting the dynamic range of electrical stimulation. This study retrospectively analyzed a clinical dataset of adult cochlear implant recipients to understand how these variables relate to speech recognition. Data from 425 implanted post-lingually deafened ears with Advanced Bionics devices were analyzed. A linear mixed-effects model was used to infer how impedance, programming and patient factors were associated with monosyllabic word recognition scores measured in quiet. Additional analyses were conducted on subsets of data to examine the role of speech processing strategy on scores, and the time taken for the scores of unilaterally implanted patients to plateau. Variation in basal impedance was negatively associated with word score, suggesting importance in evaluating the profile of impedance. While there were small, negative bivariate correlations between programming level metrics and word scores, these relationships were not clearly supported by the model that accounted for other factors. Age at implantation was negatively associated with word score, and duration of implant experience was positively associated with word score, which could help to inform candidature and guide expectations. Electrode array type was also associated with word score. Word scores measured with traditional continuous interleaved sampling and current steering speech processing strategies were similar. The word scores of unilaterally implanted patients largely plateaued within 6-months of activation. However, there was individual variation which was not related to initially measured impedance and programming levels.

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.

Separating the Novel Speech Sound Perception of Lexical Tone Chimeras From Their Auditory Signal Manipulations: Behavioral and Electroencephalographic Evidence.

Previous research has shown the novelty of lexical-tone chimeras (artificially constructed speech sounds created by combining normal speech sounds of a given language) to native speakers of the language from which the chimera components were drawn. However, the source of such novelty remains unclear. Our goal in this study was to separate the effects of chimeric tonal novelty in Mandarin speech from the effects of auditory signal manipulations. We recruited 20 native speakers of Mandarin and constructed two sets of lexical-tone chimeras by interchanging the envelopes and fine structures of both a falling/yi4/and a rising/yi2/Mandarin tone through 1, 2, 3, 4, 6, 8, 16, 32, and 64 auditory filter banks. We conducted pitch-perception ability tasks via a two-alternative, forced-choice paradigm to produce behavioral (versus physiological) pitch perception data. We also obtained electroencephalographic measurements through the scalp-recorded frequency-following response (FFR). Analyses of variances and post hoc Greenhouse-Geisser procedures revealed that the differences observed in the participants' reaction times and FFR measurements were attributable primarily to chimeric novelty rather than signal manipulation effects. These findings can be useful in assessing neuroplasticity and developing speech-processing strategies.

Perception of temporally enhanced and hearing aid processed speech in children with late-onset Auditory Neuropathy Spectrum Disorder

ObjectiveTo investigate phrase perception and subjective quality preference of temporal enhancement-based speech processing strategies: Deep-band modulation and Stretching, and hearing aid processed speech in adolescents with late-onset Auditory Neuropathy. Methods15 participants with Auditory Neuropathy Spectrum Disorder were involved. Speech perception was assessed using unprocessed, deep-band modulated, stretched, and hearing aid processed conditions. Subjective preference was also assessed using the pair-wise comparison technique. Gap detection test was done using broadband noise to investigate the possible correlation with benefit from processing strategies. ResultsAs a group, no significant benefits were found with processed speech. Clinically relevant trends emerged on subdividing the group into good and poor performers. Deep-band modulation processing was significantly better than unprocessed speech in those with poorer speech recognition abilities. There was a trend for those with poorer temporal processing abilities to benefit more with deep-band modulation processing. In those with relatively better speech recognition abilities, processing showed no benefit, and hearing aid processed speech was inferior to unprocessed speech. Quality-wise, the unprocessed speech was preferred by all the participants. Among the processed conditions, deep-band modulation was preferred by most, followed by stretching and hearing aid processed speech. ConclusionResults indicate that temporal enhancement strategies may be beneficial for a subset of individuals with ANSD with poorer temporal processing and speech perception abilities. However, processing strategies need to take into account the quality aspect and not just intelligibility.

Hearing-impaired Children and Adults in Need of Cochlear Implant- A Hospital Based Cross-sectional Study

Introduction: Hearing is essential to learn language and speech and to develop cognitive skills. According to World Health Organisation (WHO), world-wide approximately 350 million people have hearing disorder. The performance of some moderately severe hearing-impaired adults and children using hearing aids is poorer than that of even profoundly hearing-impaired individuals using cochlear implants with advanced speech processing strategies. Aim: To find out the appropriate candidates in need of cochlear implantation in Prayagraj district of Uttar Pradesh, India. Materials and Methods: This cross-sectional study was conducted on hearing impaired patients attending Ear Nose Throat (ENT) Out Patient Department (OPD) of tertiary health care center in Prayagraj Uttar Pradesh from August 2011 to July 2012. The study population consisted of 95 patients categorised into four groups (pre-lingual children and adults, post-lingual children and adults) who presented with the chief complaints of impaired hearing and delayed speech. A detailed history, clinical and other relevant systemic examination and investigations were done. Patients were subjected to free field audiometry, pure tone audiometry and Brainstem-Evoked Response Audiometry (BERA) for assessment of hearing threshold level. Patients used hearing aid for six months and after hearing aid use, their hearing threshold and speech discrimination scores were estimated. Patients, whose aided score on open-set sentence test was less than 50%, were selected as candidate for cochlear implants, as they were not significantly benefited by hearing aids. Results: Out of the 95 cases, 48 were found to be suitable for cochlear implantation, which formed 50.5% of the study group. Pre-lingual hearing impaired adults had the highest percentage i.e., 86.7%, fulfilling the criteria for cochlear implantation followed by pre-lingual children, in whom 46.7% fell in this category. A 26.7% of postlingual children and 20% of postlingual adults were found suitable for cochlear implantation. Conclusion: The pre-lingual hearing impaired children and adults are more in need for cochlear implantation than the postlingual hearing-impaired children and adults. Approximately, 134,501 cases were estimated to be, in need of cochlear implantation in Prayagraj district based on the census estimate of 2011.

Recognising foreign-accented speech of varying intelligibility and linguistic complexity: insights from older listeners with or without hearing loss

Objective The goal of this study was to assess recognition of foreign-accented speech of varying intelligibility and linguistic complexity in older adults. It is important to understand the factors that influence the recognition of this commonly encountered type of speech, in a population that remains understudied in this regard. Design A repeated measures design was used. Listeners repeated back linguistically simple and complex sentences heard in noise. The sentences were produced by three talkers of varying intelligibility: one native American English, one foreign-accented talker of high intelligibility and one foreign-accented talker of low intelligibility. Percentage word recognition in sentences was measured. Study sample Twenty-five older listeners with a range of hearing thresholds participated. Results We found a robust interaction between talker intelligibility and linguistic complexity. Recognition accuracy was higher for simple versus complex sentences, but only for the native and high intelligibility foreign-accented talkers. This pattern was present after effects of working memory capacity and hearing acuity were taken into consideration. Conclusion Older listeners exhibit qualitatively different speech processing strategies for low versus high intelligibility foreign-accented talkers. Differences in recognition accuracy for words presented in simple versus in complex sentence contexts only emerged for speech over a threshold of intelligibility.

Recognition of foreign-accented speech in noise: The interplay between talker intelligibility and linguistic structure.

Foreign-accented speech recognition is typically tested with linguistically simple materials, which offer a limited window into realistic speech processing. The present study examined the relationship between linguistic structure and talker intelligibility in several sentence-in-noise recognition experiments. Listeners transcribed simple/short and more complex/longer sentences embedded in noise. The sentences were spoken by three talkers of varying intelligibility: one native, one high-, and one low-intelligibility non-native English speakers. The effect of linguistic structure on sentence recognition accuracy was modulated by talker intelligibility. Accuracy was disadvantaged by increasing complexity only for the native and high intelligibility foreign-accented talkers, whereas no such effect was found for the low intelligibility foreign-accented talker. This pattern emerged across conditions: low and high signal-to-noise ratios, mixed and blocked stimulus presentation, and in the absence of a major cue to prosodic structure, the natural pitch contour of the sentences. Moreover, the pattern generalized to a different set of three talkers that matched the intelligibility of the original talkers. Taken together, the results in this study suggest that listeners employ qualitatively different speech processing strategies for low- versus high-intelligibility foreign-accented talkers, with sentence-related linguistic factors only emerging for speech over a threshold of intelligibility. Findings are discussed in the context of alternative accounts.

An acoustic and auditory analysis of vocants in infants with cochlear implants

Introduction The duration of the nuclei is a crucial factor for the shift of prelexical to mature speech, since control of duration is closely related with improved speech intelligibility. Objectives This work records the suprasegmental feature of duration in infants with normal hearing (NH) compared to those with cochlear implants (CI) based on vocant productions (quasivowels and full vowels). Materinals and Methods In this longitudinal study, 102 vocant productions were analyzed from cases of congenitally hearing-impaired infants (implantation ages 1:4 and 1:11 years; post-implant ages 0:6 months and 1:3 years) who were matched with three NH infants of similar hearing experience (ages 0:8–0:11 months). Current methodology analyzes vocants using a combination of acoustical and auditory analyses. Vegetative data or reflexive sounds were excluded. Participants had had unknown deafness etiology and no other disabilities. Duration was measured using wideband spectrographic analysis, from voice onset to the loss of audible signal and the decrease of higher formant’s energy. Results The results showed that the mean vocant duration of young CI users was longer, compared to hearing matched peers during the first six months after cochlear implantation. Conclusions This recorded weakness for CI users' speech production is a challenge for future work in speech processing strategies. This is the first study measuring production of vocants during the pre-linguistic stage in CI recipients.

Human Frequency Following Responses to Vocoded Speech: Amplitude Modulation Versus Amplitude Plus Frequency Modulation.

The most commonly employed speech processing strategies in cochlear implants (CIs) only extract and encode amplitude modulation (AM) in a limited number of frequency channels. proposed a novel speech processing strategy that encodes both frequency modulation (FM) and AM to improve CI performance. Using behavioral tests, they reported better speech, speaker, and tone recognition with this novel strategy than with the AM-alone strategy. Here, we used the scalp-recorded human frequency following responses (FFRs) to examine the differences in the neural representation of vocoded speech sounds with AM alone and AM + FM as the spectral and temporal cues were varied. Specifically, we were interested in determining whether the addition of FM to AM improved the neural representation of envelope periodicity (FFRENV) and temporal fine structure (FFRTFS), as reflected in the temporal pattern of the phase-locked neural activity generating the FFR. FFRs were recorded from 13 normal-hearing, adult listeners in response to the original unprocessed stimulus (a synthetic diphthong /au/ with a 110-Hz fundamental frequency or F0 and a 250-msec duration) and the 2-, 4-, 8- and 16-channel sine vocoded versions of /au/ with AM alone and AM + FM. Temporal waveforms, autocorrelation analyses, fast Fourier Transform, and stimulus-response spectral correlations were used to analyze both the strength and fidelity of the neural representation of envelope periodicity (F0) and TFS (formant structure). The periodicity strength in the FFRENV decreased more for the AM stimuli than for the relatively resilient AM + FM stimuli as the number of channels was increased. Regardless of the number of channels, a clear spectral peak of FFRENV was consistently observed at the stimulus F0 for all the AM + FM stimuli but not for the AM stimuli. Neural representation as revealed by the spectral correlation of FFRTFS was better for the AM + FM stimuli when compared to the AM stimuli. Neural representation of the time-varying formant-related harmonics as revealed by the spectral correlation was also better for the AM + FM stimuli as compared to the AM stimuli. These results are consistent with previously reported behavioral results and suggest that the AM + FM processing strategy elicited brainstem neural activity that better preserved periodicity, temporal fine structure, and time-varying spectral information than the AM processing strategy. The relatively more robust neural representation of AM + FM stimuli observed here likely contributes to the superior performance on speech, speaker, and tone recognition with the AM + FM processing strategy. Taken together, these results suggest that neural information preserved in the FFR may be used to evaluate signal processing strategies considered for CIs.

Dynamic current focusing for loudness encoding in cochlear implants: a take-home trial

Objective: This study aimed to evaluate a more energy-efficient dynamic current focussing (DCF) speech-processing strategy after long-term listening experience. In DCF, tripolar stimulation is used near the threshold and loudness is controlled by the compensation coefficient σ. A recent acute pilot study showed improved spectral-temporally modulated ripple test (SMRT) scores at low loudness levels, but battery life was reduced to 1.5–4 hours.Design: Within-subject comparisons were made for the clinical versus. DCF strategy after 5 weeks of at-home usage. Speech intelligibility in noise, spectral ripple discrimination, temporal modulation detection, loudness growth, and subjective ratings were assessed.Study sample: Twenty HiRes90K (Advanced Bionics, Valencia, USA) cochlear implant (CI) users.Results: Average battery life was 9 hours with the newly implemented DCF compared to 13.4 hours with the clinical strategy. Compared with measurements made at the beginning of the study, SMRT-scores and speech intelligibility in noise were significantly improved with DCF. However, both measures suffered from unexpected learning effects over time. The improvement disappeared and speech intelligibility in noise declined significantly relative to the final control measurement with the clinical strategy.Conclusion: Most CI users can adapt to the DCF strategy in a take-home setting. Although DCF has the potential to improve performance on the SMRT test, learning effects complicate the interpretation of the current results.

Encoding speech in cochlear implants using simultaneous amplitude and rate modulation

To improve speech perception for cochlear implant (CI) users, it is essential to improve the transmission of temporal envelopes. The most common speech processors deliver temporal envelopes via the CI using fixed-rate amplitude modulated (AM) pulse trains. Psychophysical studies suggest that rate modulation (RM) and AM are perceived by a shared temporal integration mechanism, but the potential for them to constructively combine to encode temporal envelopes has yet to be explored. In this experiment, a speech processing strategy called amplitude and rate temporal modulation was developed to encode speech temporal envelopes with simultaneous AM and RM. The strategy was tested for perception of clean speech at 60 and 40 dBA, and 60 dBA speech in noise (+10 dB SNR). The amount of RM was varied and the amount of AM was held constant to determine whether the addition of RM could enhance the perception of temporal envelopes and improve speech understanding. At the lowest RM amount, speech scores were poorest for all speech conditions. For 60 dBA clean speech and speech in noise, speech scores were significantly better at the highest RM amounts, suggesting that RM combined with AM can be used to enhance perception of temporal envelopes.

CI Programming in Patients with Neurologic Impairment

CI Programming in Patients with Neurologic Impairment

CODING AND ANALYSIS OF SPEECH IN COCHLEAR IMPLANT: A REVIEW

About 5% of the total population of world has hearing impairment and this is 6.3% in India.The hearing impairment in patients can be corrected by using a hearing aid or cochlear implant (CI) .Hearing aid is a traditional way while CI, which is surgically implanted, is a modern way to correct the hearing impairment. In comparison to hearing aids CI increases speech intelligibility at a greater level. Also speech intelligibility decreases in noise though acceptable in noise-free environments. With the advancement of technology over past decades, it shows increase in speech intelligibility with new emerging speech coding strategies. In this paper the basic speech processing strategies for speech coding and different techniques and algorithms, which aimed to increase the speech intelligibility, are being reviewed. Speech will be analyzed based on some measures like Analysis of Variation (ANOVA), Root Mean Square Error (RMSE) etc. The focus will be on speech perception and intelligibility enhancement.