Sentence Recognition Scores Research Articles

A Cochlear-Implant Processor for Encoding Music and Lowering Stimulation Power

Cochlear implants (CIs), or bionic ears, restore hearing in profoundly deaf (greater than -90 dB hearing loss) patients. They function by transforming frequency patterns in sound into corresponding spatial electrode-stimulation patterns for the auditory nerve. Over the past 20 years, improvements in sound-processing strategies, in the number of electrodes and channels, and in the rate of stimulation have yielded improved sentence and word recognition scores in patients. Next- generation implants will be fully implanted inside the patient's body. Consequently, power consumption requirements for signal processing will be very stringent.

Speech Recognition in Quiet and Noise in Borderline Cochlear Implant Candidates

The present study 1) examined speech recognition at three intensity levels and in noise for adults with bilateral hearing loss who wore amplification and were referred for cochlear implant evaluation but did not meet current audiological criteria, and 2) compared their performance to cochlear implant recipients using current implant technology. When tested at 70 dB SPL, hearing aid subjects' word and sentence recognition scores were similar to or greater than the scores of cochlear implant recipients. Compared to their implanted peers, however, subjects' scores were significantly poorer at normal (60 dB SPL) and soft (50 dB SPL) presentation levels for words and at soft levels for sentences; detection thresholds were also significantly poorer at 1000 Hz and above. The assessment of candidates at louder-than-normal levels (i.e., 70 dB SPL) may not correctly portray their day-to-day communication struggles.

Perception of Temporally Processed Speech by Listeners with Hearing Impairment

The purpose of this study was to assess a new signal-processing strategy, Spatiotemporal Pattern Correction (SPC), for a group of listeners with varying degrees of sensorineural hearing loss. SPC is based on a physiological model of the level-dependent temporal response properties of auditory nerve (AN) fibers in normal and impaired ears. SPC attempts to "correct" AN response patterns by introducing time-varying group delays that differ across frequency channels. Listeners' speech intelligibility and preference judgments were obtained at different strengths of SPC processing. Fifteen listeners, 12 with bilateral sensorineural hearing loss and 3 with normal hearing, participated in this study. Listeners with hearing impairment were separated into 3 groups (mild, moderate, and moderate-to-severe), based on their pure-tone averages at 0.5, 1, 2, and 4 kHz. All preference judgments were made using sentences from the Hearing-In-Noise-Test (HINT). The sentences were processed at five SPC strengths (1.0, 1.1, 1.2, 1.3, and 1.4). At an SPC strength of 1.0, the speech was processed through the SPC signal processor, becoming bandlimited, but no dynamic group delays were added to the signal. On each trial, listeners were presented a single sentence at two different SPC strengths, 1.0 (uncorrected) and a randomly selected SPC strength. Listeners were instructed to identify which of the two sentences they preferred. Sixteen vowel-consonant syllables, a subset of the Nonsense Syllable Test (NST), were used to assess speech intelligibility at three SPC strengths (1.0, 1.1, and 1.2). Listeners were asked to push one of 16 buttons on a response box that corresponded to the vowel-consonant syllable they heard. The moderate-to-severe hearing loss group was also tested using the low-probability sentences of the Speech-Perception-In-Noise (SPIN) test. Listeners with normal hearing and listeners with mild hearing loss preferred the quality of uncorrected sentences (SPC strength of 1.0) compared with SPC-processed sentences. As the strength of SPC increased, listeners' preference for uncorrected sentences also increased. Listeners with moderate and moderate-to-severe hearing loss had difficulty differentiating between uncorrected and lower strength SPC-processed sentences but strongly preferred the uncorrected sentences as compared with high strength SPC-processed sentences. Vowel-consonant intelligibility was not improved or degraded by SPC. Sentence recognition scores for listeners with moderate-to-severe hearing loss decreased with SPC processing. Although SPC-processed speech was not preferred by listeners with hearing loss, the listeners with a more moderate degree of impairment could not differentiate the unprocessed sentences from the SPC processed sentences. Speech intelligibility was not improved by SPC processing.

Recognition of Simulated Telephone Speech by Cochlear Implant Users

To evaluate cochlear implant users' understanding of telephone speech. Telephone speech was simulated by band-limiting broadband speech stimuli. Multitalker vowel, consonant, and sentence recognition was measured for both simulated telephone speech and broadband speech in 10 postlingually deafened adult cochlear implant users. The study was approved by the St. Vincent's Hospital institutional review board, and signed, informed consent was obtained from all participants. There was no significant difference in vowel recognition scores between broadband and telephone speech. However, mean consonant and sentence recognition scores were significantly poorer with telephone speech. The limited telephone bandwidth significantly reduced cochlear implant users' understanding of telephone speech. The effect of band-limited speech was highly variable, suggesting that the contribution of high-frequency information to speech recognition varied significantly among the cochlear implant users.

Solutions to electromagnetic interference problems between cochlear implants and GSM phones

For persons using cochlear implants, electromagnetic compatibility (EMC) problems may sometimes be an obstacle to using digital cellular telephones. This study aimed at exploring the benefit of three new assistive listening device prototypes that eliminate or diminish EMC problems. Ten experienced cochlear implant users listened in quiet to running speech samples and a sentence test on a landline phone, a digital cellular phone with and without three prototypes. The subjects' performance was assessed using a sentence test, a subjective visual analog scale, and by ranking the best and the poorest listening condition. Compared to the other test conditions, listening to a digital cellular phone alone revealed, on average, the poorest sentence recognition scores (29%) and the poorest results in four different subjective judgments (the amount of disturbances, the clarity of the message, the quality of the sound, overall judgment) with all three implant systems tested. The prototypes generally helped the implantees to recognize speech better on the cellular telephone (by 10-21 percent units, on average). Use of assistive listening devices and further development of EMC of both cochlear implant systems and digital cellular phones needs to take place to enable smooth use of digital cellular phones for all implantees.

Subspace algorithms for noise reduction in cochlear implants

A single-channel algorithm is proposed for noise reduction in cochlear implants. The proposed algorithm is based on subspace principles and projects the noisy speech vector onto "signal" and "noise" subspaces. An estimate of the clean signal is made by retaining only the components in the signal subspace. The performance of the subspace reduction algorithm is evaluated using 14 subjects wearing the Clarion device. Results indicated that the subspace algorithm produced significant improvements in sentence recognition scores compared to the subjects' daily strategy, at least in stationary noise. Further work is needed to extend the subspace algorithm to nonstationary noise environments.

Comparison of speech perception performance between the nucleus 24 and nucleus 24 contour cochlear implant systems

Objective—To compare the 1-, 3-, and 6-month postoperative speech perception scores obtained by a group of subjects who received the new perimodiolar array (Nucleus Contour) cochlear implant with those obtained by a group of subjects implanted with the straight electrodes of the previous-generation Nucleus 24 device.Material and Methods—The speech performance of 10 postlingually deafened adults implanted with the Nucleus Contour device was compared with that of matched controls who received the Nucleus 24 model. Objective measures included word and sentence speech recognition scores.Results—Patients implanted with the Nucleus Contour device obtained significantly higher word and sentence recognition scores after short-term use of the implant compared to those obtained by patients implanted with the Nucleus 24 model.Conclusion—Further long-term studies are required to determine whether the Nucleus Contour CI recipients continue to improve over time.

Frequency-place compression and expansion in cochlear implant listeners

In multichannel cochlear implants, low frequency information is delivered to apical cochlear locations while high frequency information is delivered to more basal locations, mimicking the normal acoustic tonotopic organization of the auditory nerves. In clinical practice, little attention has been paid to the distribution of acoustic input across the electrodes of an individual patient that might vary in terms of spacing and absolute tonotopic location. In normal-hearing listeners, Başkent and Shannon (J. Acoust. Soc. Am. 113, 2003) simulated implant signal processing conditions in which the frequency range assigned to the array was systematically made wider or narrower than the simulated stimulation range in the cochlea, resulting in frequency-place compression or expansion, respectively. In general, the best speech recognition was obtained when the input acoustic information was delivered to the matching tonotopic place in the cochlea with least frequency-place distortion. The present study measured phoneme and sentence recognition scores with similar frequency-place manipulations in six Med-El Combi 40+ implant subjects. Stimulation locations were estimated using the Greenwood mapping function based on the estimated electrode insertion depth. Results from frequency-place compression and expansion with implants were similar to simulation results, especially for postlingually deafened subjects, despite the uncertainty in the actual stimulation sites of the auditory nerves. The present study shows that frequency-place mapping is an important factor in implant performance and an individual implant patient's map could be optimized with functional tests using frequency-place manipulations.

Cochlear implant failure: is an auditory brainstem implant the answer?

ObjectiveTo investigate the auditory rehabilitative results achieved in five patients with cochlear implants (CIs) whosubsequently received, due to poor results, auditory brainstem implants (ABIs). Material and MethodsBetween April 1997 and March 2003, 37 patients (age range 14 months to 70 years) were fitted withABIs in our ENT Department. Fourteen subjects had neurofibromatosis type 2 and 23 were non-tumor patients who hadcochlea or cochlear nerve disease. Five subjects had previously been treated with a CI and received an ABI owing to the poorresults achieved. One child had bilateral undiagnosed cochlear nerve aplasia and one was suffering from auditoryneuropathy; three adults had total cochlear ossification. ResultsThe open-set sentence recognition score (auditory-only mode) 6–8 months after ABI activation ranged from 0% to100% in adults. In 1 subject the speech-tracking score was 56 words/min with the ABI. The two children who had achievedno hearing ability with their CI were able to detect sounds and words as early as 3 months after activation of the ABI. Conclusion CI failure as a result of anatomical abnormalities can be remedied by an ABI.

Hearing aid users benefit from induction loop when using digital cellular phones.

Hearing aid users have recently been reported to experience problems with electromagnetic interference when using digital cellular phones. This study was undertaken to investigate the possible benefit of an induction loop system developed for use with some cellular phone models, and also to compare the possible benefit in two languages (Finnish and American English) as well as the benefit with two hearing aid technologies (analog versus digital). The study was performed in controlled laboratory conditions at two tertiary care hearing health care centers, one in Oulu, Finland and the other in Dallas, in the United States. The subjects were experienced users of behind-the-ear hearing aids and served as their own controls in three different listening conditions. Thirty-two eligible subjects (20 in Oulu and 12 in Dallas) participated in three test conditions: 1. call with a landline phone, 2. call with a digital cellular phone alone and 3. call with a digital cellular phone coupled to an induction loop. Sentence recognition scores and subjective judgments using a visual analog scale revealed the poorest results with the digital cellular phone alone. When the induction loop was used with the digital cellular phones, sentence recognition scores and the visual analog scale scores were comparable to the scores obtained with a landline phone. The mean sentence recognition score for analog hearing aids was 62.4% (95% confidence interval 50.2 to 74.6) with the landline phone, 12.6% (-1.6 to 26.9) with the digital cellular phone alone, and 63.3% (44.2 to 82.3) when using the digital cellular phone with the induction loop. For digital hearing aids, the sentence recognition scores were 62.4% (51.9 to 72.9), 37.4% (18.0 to 56.8) and 57.6% (39.0 to 76.2), respectively. There was no significant difference in performance between the two centers. However, when using the digital cellular phone alone, there was no drop in the sentence recognition scores with the few (N = 5) digital hearing aids in Dallas. The subjects ranked the digital cellular phone alone as the poorest test condition and the digital cellular phone with an induction loop as the best. Induction loops appear to offer one possible solution for the incompatibility problem between hearing aids and digital cellular phones. However, the generalizability of the results must be viewed cautiously, because testing included only one induction loop and two digital cellular phone models.

Speech coding strategies and revised cochlear implant candidacy: an analysis of post-implant performance.

Technological advances in cochlear implant systems on which a sequence of speech coding strategies have been implemented seem to have resulted in improved speech perception. However, changing selection criteria for implantation have coincided with evolving technology and may confound post-implantation speech perception performance. This study compares speech coding strategy with speech perception performance in severe and profound postlingually deafened adults using one of three successive generations of Nucleus Cochlear Implant speech processors (i.e., Mini Speech Processor, Spectra 22, and SPrint) implementing three speech coding strategies (i.e., MPEAK, SPEAK, and Advanced Combination Encoders; Cochlear Corporation, Englewood, CO, U.S.A.). Four cohorts of patients were retrospectively reviewed. Multicenter, tertiary referral cochlear implant programs in Ontario, Canada. Four cohorts of patients (n = 139) were identified based on preimplant audiological measures, duration of deafness, device type, and speech coding strategy. Word and sentence recognition scores at 12 months after implantation were compared using MPEAK with SPEAK22 implemented on the Nucleus 22 speech processors (Mini Speech Processor and Spectra22, respectively) and SPEAK24 as well as Advanced Combination Encoders implemented on the Nucleus 24 SPrint processor. Open-set speech recognition batteries revealed significant improvements in word and sentence scores as advancing technology implemented new speech coding strategies. Subgroup analysis of profoundly deafened patients supported this. Analysis of covariance confirmed that the measured differences could not be accounted for by changing selection criteria for implantation. Improvements in performance can be attributed to evolving speech coding strategies and speech processors rather than to differences in preimplant candidacy.

Multichannel cochlear implantation in radical mastoidectomy cavities.

We report on our experience in cochlear implantation in patients with radical mastoidectomy cavities. Study Design, Setting, and Methods: Retrospectively, records of patients from the Department of Otolaryngology, University of Parma between December 1991 and March 2000 were reviewed, and 6 postlingually deafened adults who received a cochlear implant in a radical cavity were identified. Speech performances were evaluated in terms of bisyllabic word and sentence recognition and common phrase comprehension. To date, with a follow-up of 1 to 9 years, no patient has experienced extrusion of electrodes or other local or intracranial complications. Mean bisyllabic word and sentence recognition scores were 74% and 80%, respectively. Mean comprehension score for common phrases was 86%. By obliterating and isolating the radical mastoidectomy cavity from the outer environment, patients who previously had undergone radical surgery of the middle ear can be safely implanted with satisfactory hearing results.

Evaluation of context effects in sentence recognition.

It was investigated whether the model for context effects, developed earlier by Bronkhorst et al. [J. Acoust. Soc. Am. 93, 499-509 (1993)], can be applied to results of sentence tests, used for the evaluation of speech recognition. Data for two German sentence tests, that differed with respect to their semantic content, were analyzed. They had been obtained from normal-hearing listeners using adaptive paradigms in which the signal-to-noise ratio was varied. It appeared that the model can accurately reproduce the complete pattern of scores as a function of signal-to-noise ratio: both sentence recognition scores and proportions of incomplete responses. In addition, it is shown that the model can provide a better account of the relationship between average word recognition probability (p(e)) and sentence recognition probability (p(w)) than the relationship p(w) =p(e)j, which has been used in previous studies. Analysis of the relationship between j and the model parameters shows that j is, nevertheless, a very useful parameter, especially when it is combined with the parameter j', which can be derived using the equivalent relationship p(w,0) = (1 - p(e))(j'), where p(w,0) is the probability of recognizing none of the words in the sentence. These parameters not only provide complementary information on context effects present in the speech material, but they also can be used to estimate the model parameters. Because the model can be applied to both speech and printed text, an experiment was conducted in which part of the sentences was presented orthographically with 1-3 missing words. The results revealed a large difference between the values of the model parameters for the two presentation modes. This is probably due to the fact that, with speech, subjects can reduce the number of alternatives for a certain word using partial information that they have perceived (i.e., not only using the sentence context). A method for mapping model parameters from one mode to the other is suggested, but the validity of this approach has to be confirmed with additional data.

Rehabilitation of hearing and communication functions in patients with NF2.

Most patients with neurofibromatosis type 2 (NF2) lose hearing either spontaneously or after removal of their neurofibromas. The patient may benefit from conventional hearing aids if, due to modern microsurgery and intraoperative monitoring the integrity of the cochlea and the 8th nerve is preserved. With lost auditory function but preserved electrical stimulibility of the 8th nerve a cochlear implant may be appropriate. But if the patients have no remaining 8th nerve to stimulate, there is no benefit from cochlear implants. Until some years ago, vibrotactile aids, lip-reading, and sign language have been the only communication modes available to these patients. With auditory brain stem implants it is now possible to bypass both the cochlea and the 8th nerve and to stimulate the cochlear nucleus directly. Stimulation of the devices produces useful auditory sensations in almost all patients. Testing of perceptual performance indicated significant benefit from the device for communication purposes, including sound-only sentence recognition scores and the ability to converse on the telephone. Also lip-reading is significantly improved with brain stem implants. The successful work of an auditory brainstem program center depends very much on the close interdisciplinary collaboration between the Departments of Neurosurgery and ENT-surgery. In the future new developments like speech processing strategies and new designed electrodes accessing the complex tonotopic organization of the cochlear nucleus may further improve rehabilitation in these patients who would have been deaf some years ago.

Use of audiovisual information in speech perception by prelingually deaf children with cochlear implants: a first report.

Although there has been a great deal of recent empirical work and new theoretical interest in audiovisual speech perception in both normal-hearing and hearing-impaired adults, relatively little is known about the development of these abilities and skills in deaf children with cochlear implants. This study examined how prelingually deafened children combine visual information available in the talker's face with auditory speech cues provided by their cochlear implants to enhance spoken language comprehension. Twenty-seven hearing-impaired children who use cochlear implants identified spoken sentences presented under auditory-alone and audiovisual conditions. Five additional measures of spoken word recognition performance were used to assess auditory-alone speech perception skills. A measure of speech intelligibility was also obtained to assess the speech production abilities of these children. A measure of audiovisual gain, "Ra," was computed using sentence recognition scores in auditory-alone and audiovisual conditions. Another measure of audiovisual gain, "Rv," was computed using scores in visual-alone and audiovisual conditions. The results indicated that children who were better at recognizing isolated spoken words through listening alone were also better at combining the complementary sensory information about speech articulation available under audiovisual stimulation. In addition, we found that children who received more benefit from audiovisual presentation also produced more intelligible speech, suggesting a close link between speech perception and production and a common underlying linguistic basis for audiovisual enhancement effects. Finally, an examination of the distribution of children enrolled in Oral Communication (OC) and Total Communication (TC) indicated that OC children tended to score higher on measures of audiovisual gain, spoken word recognition, and speech intelligibility. The relationships observed between auditory-alone speech perception, audiovisual benefit, and speech intelligibility indicate that these abilities are not based on independent language skills, but instead reflect a common source of linguistic knowledge, used in both perception and production, that is based on the dynamic, articulatory motions of the vocal tract. The effects of communication mode demonstrate the important contribution of early sensory experience to perceptual development, specifically, language acquisition and the use of phonological processing skills. Intervention and treatment programs that aim to increase receptive and productive spoken language skills, therefore, may wish to emphasize the inherent cross-correlations that exist between auditory and visual sources of information in speech perception.

Does choosing the "worse" ear for cochlear implantation affect outcome?

To determine whether choosing the "better" ear or the "worse" ear for cochlear implantation impacts performance outcome. Retrospective cohort study. University teaching hospital-cochlear implant program. Two groups of cochlear implantees were selected and matched based on clinical parameters, including duration of deafness/age at implantation, implant types, and processing strategies. Nineteen patients received an implant in his or her "better" ear of the two that had been amplified. An equal number of patients received an implant in the "worse" ear--an ear that was not amplified or was chosen to avoid causing oscillopsia; or if the patient was not willing to relinquish his or her hearing aid in the "better" ear based on subjective or objective criteria. Standard speech perception testing was performed. The average open-set speech perception responses at 1 year after implantation were as follows: word recognition score 40.4% and sentence recognition score 81% in the aided subjects (better ears); word recognition score 41.5% and sentence recognition score 84.5% in the unaided group (worse ears). No differences were found between the two groups of implantees. Choosing the "worse" ear for implantation did not appear to have a negative impact on performance outcome in this match-paired study.

The recognition of isolated words and words in sentences: individual variability in the use of sentence context.

Estimates of the ability to make use of sentence context in 34 postlingually hearing-impaired (HI) individuals were obtained using formulas developed by Boothroyd and Nittrouer [Boothroyd and Nittrouer, J. Acoust. Sco. Am. 84, 101-114 (1988)] which relate scores for isolated words to words in meaningful sentences. Sentence materials were constructed by concatenating digitized productions of isolated words to ensure physical equivalence among the test items in the two conditions. Isolated words and words in sentences were tested at three levels of intelligibility (targeting 29%, 50%, and 79% correct). Thus, for each subject, three estimates of context ability, or k factors, were obtained. In addition, auditory, visual, and auditory-visual sentence recognition was evaluated using natural productions of sentence materials. Two main questions were addressed: (1) Is context ability constant for speech materials produced with different degrees of clarity? and (2) What are the relations between individual estimates of k and sentence recognition as a function of presentation modality? Results showed that estimates of k were not constant across different levels of intelligibility: k was greater for the more degraded condition relative to conditions of higher word intelligibility. Estimates of k also were influenced strongly by the test order of isolated words and words in sentences. That is, prior exposure to words in sentences improved later recognition of the same words when presented in isolation (and vice versa), even though the 1500 key words comprising the test materials were presented under degraded (filtered) conditions without feedback. The impact of this order effect was to reduce individual estimates of k for subjects exposed to sentence materials first and to increase estimates of k for subjects exposed to isolated words first. Finally, significant relationships were found between individual k scores and sentence recognition scores in all three presentation modalities, suggesting that k is a useful measure of individual differences in the ability to use sentence context.

The multichannel auditory brain stem implant: Performance in twenty patients

The auditory brain stem implant has been used effectively to provide hearing sensations to individuals deafened by bilateral auditory nerve tumors (neurofibromatosis type 2). During tumor removal, the auditory brain stem implant is implanted into the lateral recess of the fourth ventricle by a translabyrinthine approach and is intended to stimulate auditory neurons of the cochlear nucleus complex. A new eight-electrode multichannel auditory brain stem implant was developed and evaluated in 20 patients who had at least 3 months’ experience with the device. Mild nonauditory sensations (primarily tingling in the head or torso) were encountered in some instances but could be managed by changing the stimulus characteristics or excluding electrodes. Testing of perceptual performance indicated significant benefit from the device for communication purposes, including sound-only sentence recognition scores in three patients ranging from 49% to 58% and ability to converse on the telephone. These results indicate that significant auditory benefit can be derived from direct multichannel electrical stimulation of the auditory portion of the human brain stem. (Otolaryngol Head Neck Surg 1998;118:291-303.)

The multichannel auditory brain stem implant: performance in twenty patients.

The auditory brain stem implant has been used effectively to provide hearing sensations to individuals deafened by bilateral auditory nerve tumors (neurofibromatosis type 2). During tumor removal, the auditory brain stem implant is implanted into the lateral recess of the fourth ventricle by a translabyrinthine approach and is intended to stimulate auditory neurons of the cochlear nucleus complex. A new eight-electrode multichannel auditory brain stem implant was developed and evaluated in 20 patients who had at least 3 months' experience with the device. Mild nonauditory sensations (primarily tingling in the head or torso) were encountered in some instances but could be managed by changing the stimulus characteristics or excluding electrodes. Testing of perceptual performance indicated significant benefit from the device for communication purposes, including sound-only sentence recognition scores in three patients ranging from 49% to 58% and ability to converse on the telephone. These results indicate that significant auditory benefit can be derived from direct multichannel electrical stimulation of the auditory portion of the human brain stem.

Recall of sentence meaning in aphasic and nonaphasic adults

The hypothesis that memory for spoken sentences is facilitated by memory for sentence meaning was tested with 16 aphasic and 8 nonaphasic adults. Subjects were asked to make judgments of same or different on pairs of active and passive sentences separated in time. Sentence pairs were either identical in all respects or identical in just grammatical structure, subject-verb-object word order, or meaning. Nonaphasic subjects had higher sentence recognition scores and larger percentages of meaning preserving responses than aphasic subjects. Aphasic subjects with the highest recognition scores made more meaning preserving responses than aphasic subjects with the lowest recognition scores. The results suggested that memory for spoken sentences is facilitated more by memory for sentence meaning than memory for structure of wording.