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M W Skinner

Publications and source records attributed to M W Skinner.

At least 37 records · Page 2Linked to original sources
PubMed1997

Effects of formant bandwidth on the identification of synthetic vowels by cochlear implant recipients.

OBJECTIVE: The main objective was to investigate whether the broadening and narrowing of formant bandwidths had a significant effect on the identification of vowels often confused by Nucleus cochlear implant recipients using the Spectral Peak (SPEAK) speech coding strategy. Specifically, identification performance for synthetic vowels with the first two formants (F1 and F2) parametrically varied in bandwidth was explored. DESIGN: Eight implanted subjects identified synthetic versions of the isolated vowel sounds [I, epsilon, lambda, [symbol: see text]] with F1 and F2 bandwidth manipulations, as well as foil tokens of [i, u, a, ae, [symbol: see text]]. Identification performance was examined in terms of percent correct as well as error patterns. Further analyses compared patterns of electrode activation. RESULTS: In general, broader F1 bandwidths yielded poorer performance and narrower F1 bandwidths yielded better performance relative to identifications for the reference stimuli. However, similar manipulations of F2 bandwidths resulted in less predictable performance. Comparison of electrode activation patterns indicated a distinct sharpening or flattening in the F1 frequency region for subjects with the greatest performance extremes. CONCLUSIONS: Manipulation of F1 bandwidth can result in concomitant changes in electrode activation patterns and identification performance. This suggests that modifications in the SPEAK coding strategy for the F1 region may be a consideration. Similar manipulations of F2 bandwidth yielded less predictable results and require further investigation.

Adolescent↗
PubMed1997

Speech recognition at simulated soft, conversational, and raised-to-loud vocal efforts by adults with cochlear implants.

Ten postlinguistically deaf adults who used the Nucleus Cochlear Implant System and SPEAK speech coding strategy responded to vowels, consonants, words, and sentences presented sound-only at 70, 60, and 50 dB sound-pressure level. Highest group mean scores were at a raised-to-loud level of 70 dB for consonants (73%), words (44%), and sentences (87%); the highest score for vowels (70%) was at a conversational level of 60 dB. Lowest group mean scores were at a soft level of 50 dB for vowels (56%), consonants (47%), words (10%), and sentences (29%); all except subject 7 had some open-set speech recognition at this level. For the conversational level (60 dB), group mean scores for sentences and words were 72% and 29%, respectively. With this performance and sound-pressure level, it was observed that these subjects communicated successfully in a variety of listening situations. Given these subjects' speech recognition scores at 60 dB and the fact that 70 dB does not simulate the vocal effort used in everyday speaking situations, it is suggested that cochlear implant candidates and implantees be evaluated with speech tests presented at 60 dB instead of the customary 70 dB sound-pressure level to simulate benefit provided by implants in everyday life. Analysis of individuals' scores at the three levels for the four speech materials revealed different patterns of speech recognition among subjects (e.g., subjects 1 and 5). Future research on the relation between stimuli, sound processing, and subjects' responses associated with these different patterns may provide guidelines to select parameter values with which to map incoming sound onto an individual's electrical dynamic range between threshold and maximum acceptable loudness level to improve speech recognition.

Adult↗
PubMed1996

Identification of speech by cochlear implant recipients with the Multipeak (MPEAK) and Spectral Peak (SPEAK) speech coding strategies. I. Vowels.

OBJECTIVE: The main objective was to evaluate differences in performance associated with the two speech coding strategies. To achieve this objective, acoustic and electrical analyses of vowels identified by cochlear implant recipients were compared with their responses when they used the Multipeak (MPEAK) and the Spectral Peak (SPEAK) speech coding strategies of the Nucleus Cochlear Implant System. DESIGN: Nine subjects identified pure and r-colored English vowels with the two speech coding strategies. The two processing strategies were compared using an ABAB design. Evaluations were conducted at two weekly sessions after at least 3 wk of use with each strategy. RESULTS: Group vowel identification scores with the MPEAK versus the SPEAK strategy were not significantly different (72.3% and 73.4%, respectively). However, hierarchical loglinear analysis of group data showed that transmitted information of r-color, duration, and second-formant features was significantly better with the SPEAK than with the MPEAK strategy. In contrast, identification of the first formant feature was significantly better with the MPEAK than with the SPEAK strategy. Individual subjects had different error patterns in response to the 14 vowels. CONCLUSIONS: Electrical stimulation with the SPEAK strategy provides clearer spectral representation of second formant and duration information as well as second and third formant change in r-colored vowels than with the MPEAK strategy. Consequently, there was marked improvement in recognition of r-colored vowels with SPEAK compared with MPEAK. In contrast, transmitted information for first-formant features was significantly less with SPEAK than with MPEAK. This may have occurred because four instead of six to eight electrodes were assigned to first formant frequencies with SPEAK versus MPEAK.

Adult↗
PubMed1996

Unwrapping Cochlear implants by spiral CT.

Multielectrode, intracochlear implants were designed for individuals with profound sensorineural hearing loss who derive little or no benefit form acoustic hearing aids. Determination of each electrode's position in a patient's inner ear may improve speech processor programming to maximize speech recognition. In this paper, an approach is described to use as input a volumetric spiral computed tomography (CT) image of the Nucleus electrode array (Cochlear Pty. Ltd, Lane Cove, NSW, Australia) to unwrap it, and to measure its implanted length given starting and end points. Representative curvilinear structures were digitally synthesized in image volumes of isotropic 0.1-mm voxels. The electrode array was spirally CT-scanned in vitro and in vivo, and reconstructed on an isotropic grid in 0.1-mm steps. Two algorithms were constructed to track and measure these curvilinear structures. The first algorithm is Karhunen-Loeve (K-L)-transform based, in which the K-L transform is locally applied at a current main axis position to determine the eigenvectors of the main axis voxels, the next main axis position is estimated from the current position along the principal eigendirection, adjusted to the mass center of the orthogonal cross section passing through the estimated position, and then scaled to have a prespecified step. The second algorithm is similar to the first one but avoids use of the K-L transform. In the second algorithm, the next position is directly estimated along the local direction and then processed with the same correction and scaling operations. With user-specified starting and end points as well as a local direction at the starting point, a curvilinear structure can be automatically tracked using either of the algorithms. The first algorithm is more robust, while the second one is more efficient. In the numerical and in vitro studies, the lengths of the curvilinear structures were accurately measured. Given local directions determined in the tracking process, an electrode array image can be unwrapped into a linear array with the central electrode axis as the abscissa. The unwrapping approach allows longitudinally and cross-sectionally accurate measurement and better visualization of cochlear implant images. With preimplantation knowledge of length, width, and center electrode distance, the position of individual electrodes can be estimated after unwrapping.

Algorithms↗
PubMed1995

Temporal bone volumetric image deblurring in spiral computed tomography scanning.

RATIONALE AND OBJECTIVES: We developed a method for volumetric image deblurring in spiral (helical) computed tomography (CT) scanning with a three-dimensional (3D) Gaussian point spread function (PSF) to improve the quality of temporal bone spiral CT images for assessing the position of cochlear implants electrodes. METHODS: A patient was scanned after cochlear implantation, and the temporal bone was reconstructed into a volume with 128 voxels per dimension, 0.1 mm per voxel side, and x 10 gray-scale expansion. The 3D PSF in spiral CT imaging was assumed to be Gaussian separable transversely and longitudinally. Standard deviations of the PSF were derived and subjectively adjusted. The image was then deconvolved using Wiener filtering and maximum-likelihood deconvolution methods. Image quality was assessed both visually and quantitatively using cross-sectional area at half of the maximum (CAHM) of the implanted array as the figure of merit. RESULTS: Substantial image deblurring was achieved via deconvolution. Subjectively, anatomic structures were more clearly shown. Deconvolution reduced the CAHM by approximately one third, on average. Three-dimensional deconvolution had better image quality than two-dimensional deconvolution. The maximum-likelihood method produced superior image quality but took longer to process relative to Wiener filtering. CONCLUSION: Volumetric image deblurring is practical with a Gaussian PSF. The maximum-likelihood method is preferred if time permits. Deconvolution facilitates the study of fine details of the temporal bone and cochlear implant.

Adult↗
PubMed1995

Comparison of procedures for obtaining thresholds and maximum acceptable loudness levels with the nucleus cochlear implant system.

Two stimulus paradigms and two presentation methods were combined to form three procedures (keyboard, knob, and ascending loudness judgments with knob [ALJK]) to obtain detection thresholds and maximum acceptable loudness levels (MALs) from 11 adults with the Nucleus cochlear implant. Thresholds at which subjects correctly counted the number of stimulus bursts also were obtained. Keyboard detection thresholds were higher (Scheffé, p = .01) than knob and ALJK detection thresholds. Counted thresholds were obtained most efficiently by using keyboard detection thresholds as the initial level for testing. Keyboard MALs were highest, knob MALs intermediate, and ALJK MALs lowest (Scheffé, p = .001). MALs were obtained most efficiently with the ALJK procedure. Implications of these results for clinical practice are discussed.

Adult↗
PubMed1995

Use of test-retest measures to evaluate performance stability in adults with cochlear implants.

OBJECTIVE: This study was designed to evaluate performance stability with test-retest measures of electrical thresholds, electrical maximum acceptable loudness levels, sound-field thresholds, and audition-only speech tests. The hypothesis was that the standard error of measurement differs from one individual to another for each test, and therefore test-retest measures need to be obtained from each subject. DESIGN: Test-retest data were obtained in three sets. For the first two sets, data were obtained over 4 successive weeks to determine day-to-day variability. The third set was obtained on 2 successive days, 2 to 10 months later at each subject's annual evaluation. The seven subjects were recipients of the Nucleus cochlear implant and used the Mini Speech Processor at least one year. They were selected because they were available for research testing. RESULTS: The ranges of electrical thresholds and maximum acceptable loudness levels obtained from each subject during the first two sets were substantially larger on some electrodes than on others. Between set 1 and set 2 for each subject, there were significant differences between thresholds and between maximum acceptable loudness levels on some electrodes. For thresholds as well as maximum acceptable loudness levels, the standard error of measurement across the three sets and 10 electrodes differed among subjects. The group standard error of measurement for sound-field thresholds was small (2 dB). The group standard error of measurement for the NU-6 word test scored according to phonemes (2.75%) was less than half that for the vowel (6.06%) and consonant (5.67%) tests. The standard error of measurement for each speech test differed among subjects. CONCLUSIONS: The standard error of measurement for thresholds as well as maximum acceptable loudness levels varies among electrodes in the same subject and among subjects across electrodes. The standard error of measurement also varies among speech tests for the group as well as among subjects for each speech test. There is little variation in test-retest measures of sound-field thresholds among subjects. These results suggest the clinical importance of obtaining test-retest measures for evaluating the stability of electrical thresholds, electrical maximum acceptable loudness levels, and speech tests.

Adult↗
PubMed1994

Determination of the position of nucleus cochlear implant electrodes in the inner ear.

Accurate determination of intracochlear electrode position in patients with cochlear implants could provide a basis for detecting migration of the implant and could aid in the selection of stimulation parameters for sound processor programming. New computer algorithms for submillimeter resolution and 3-D reconstruction from spiral computed tomographic (CT) scans now make it possible to accurately determine the position of implanted electrodes within the cochlear canal. The accuracy of these algorithms was tested using an electrode array placed in a phantom model. Measurements of electrode length and interelectrode distance from spiral CT scan reconstructions were in close agreement with those from stereo microscopy. Although apparent electrode width was increased on CT scans due to partial volume averaging, a correction factor was developed for measurements from conventional radiographs and an expanded CT absorption value scale added to detect the presence of platinum electrodes and wires. The length of the cochlear canal was calculated from preoperative spiral CT scans for one patient, and the length of insertion of the electrode array was calculated from her postoperative spiral CT scans. The cross-sectional position of electrodes in relation to the outer bony wall and modiolus was measured and plotted as a function of distance with the electrode width correction applied.

Adult↗
PubMed1994

Evaluation of a new spectral peak coding strategy for the Nucleus 22 Channel Cochlear Implant System.

Sixty-three postlinguistically deaf adults from four English-speaking countries participated in a 17-week field study of performance with a new speech coding strategy, Spectral Peak (SPEAK), and the most widely used strategy, Multipeak (MPEAK), both of which are implemented on wearable speech processors of the Nucleus 22 Channel Cochlear Implant System; MPEAK is a feature-extraction strategy, whereas SPEAK is a filterbank strategy. Subjects' performance was evaluated with an experimental design in which use of each strategy was reversed and replicated (ABAB). Average scores for speech tests presented sound-only at 70 dB SPL were higher with the SPEAK strategy than with the MPEAK strategy. For tests in quiet, mean scores for medial vowels were 74.8 percent versus 70.1 percent; for medial consonants, 68.6 percent versus 56.6 percent; for monosyllabic words, 33.8 percent versus 24.6 percent; and for sentences, 77.5 percent versus 67.4 percent. For tests in noise, mean scores for Four-Choice Spondees at +10 and +5 dB signal-to-noise ratio (S/N) were 88.5 percent versus 73.6 percent and 80.1 percent versus 62.3 percent, respectively; and for sentences at +15 dB, +10, and +5 dB S/N, 66.5 percent versus 43.4 percent, 61.5 percent versus 37.1 percent, and 60.4 percent versus 31.7 percent, respectively. Subjects showed marked improvement in recognition of sentences in noise with the new SPEAK filterbank strategy. These results agree closely with subjects' responses to a questionnaire on which approximately 80 percent reported they heard best with the SPEAK strategy for everyday listening situations.

Adult↗
PubMed1992

Study of the performance of four prelinguistically or perilinguistically deaf patients with a multi-electrode, intracochlear implant.

Individuals who are born deaf or become deaf in early childhood and are implanted as adults (or in late adolescence) with a multi-electrode, intracochlear implant often cannot understand speech by audition alone. Test results of four implanted patients were analyzed to determine 1. if there was a difference in performance between patients; 2. if there was a relation between performance and history of auditory stimulation; and 3. which tests revealed performance differences. On audition-only and audition-plus-vision tests, overall performance was rank-ordered from lowest to highest for patients 1, 2, 3, and 4, respectively. Patient 4 recognized a few words audition-only. Patients 1 and 2 had long periods of no auditory stimulation; patients 3 and 4 had long periods of auditory stimulation with hearing aids prior to implantation. Tests not revealing differences in performance were identified.

Adolescent↗
PubMed1992

Recent trends in the selection and fitting of hearing aids.

A large segment of the hearing impaired population does not utilize amplification. this paper reviews several factors which may account for the under-utilization of hearing aids by the hearing impaired population. In addition, this paper reviews several recent developments in procedures used to select and fit hearing aids.

Hearing Aids↗
PubMed1991

Performance of postlinguistically deaf adults with the Wearable Speech Processor (WSP III) and Mini Speech Processor (MSP) of the Nucleus Multi-Electrode Cochlear Implant.

Seven postlinguistically deaf adults implanted with the Nucleus Multi-Electrode Cochlear Implant participated in an evaluation of speech perception performance with three speech processors: the Wearable Speech Process (WSP III), a prototype of the Mini Speech Processor, and the Mini Speech Processor. The first experiment was performed with the prototype and Wearable Speech Processor both programmed using the F0F1F2 speech coding strategy. The second experiment compared performance with the Mini Speech Processor programmed with the Multi-Peak speech coding strategy and the Wearable Speech Processor programmed with the F0F1F2 speech coding strategy. Performance was evaluated in the sound-only condition using recorded speech tests presented in quiet and in noise. Questionnaires and informal reports provided information about use in everyday life. In experiment I, there was no significant difference in performance using the Wearable Speech Processor and prototype on any of the tests. Nevertheless, six out of seven subjects preferred the prototype for use in everyday life. In experiment II, performance on open-set tests in quiet and noise was significantly higher with the Mini Speech Processor (Multi-Peak speech coding strategy) than with the Wearable Speech Processor. Subjects reported an increase in their ability to communicate with other people using the Mini Speech Processor (Multi-Peak speech coding strategy) compared with the Wearable Speech Processor in everyday life.

Adult↗
PubMed1988

Comparison of benefit from vibrotactile aid and cochlear implant for postlinguistically deaf adults.

Four postlinguistically deaf adults were evaluated presurgically with a one- or two-channel vibrotactile aid and postsurgically with a multichannel, multielectrode, intracochlear implant. Although the vibrotactile aid provided awareness of sound and enhanced flow of conversation, benefit to lipreading was small on videotaped tests and speech tracking. Scores on recorded, sound-only speech tests were not significantly above chance except in discrimination of noise from voice. With the cochlear implant, benefit to lipreading was significantly greater than with the vibrotactile aid, and scores on sound-only tests were significantly above chance. Communication was markedly better with the implant than with the vibrotactile aid. In counseling those who get no benefit from a hearing aid, the results of this study provide data on the amount of benefit one- or two-channel vibrotactile aids provide postlinguistically deaf adults who are subsequently implanted.

Adult↗
PubMed1985

Effect of amplification on the intelligibility of speech produced with an electrolarynx.

The purpose of this study was to look at the effect of orolabial amplification on the intelligibility of speech spoken with a neck model electrolarynx for two distance conditions, three noise conditions, and in relative quiet. A speaker using a neck model electrolarynx read single-answer questions to six listeners. The questions were read with and without amplification at 1.5 and 2.5 m distance, in relative quiet as well as in 66 dB, 72 dB, and 76 dBSPL (A-weighted) prerecorded cafeteria noise. The results of the study showed that speech-to-noise ratios were improved for amplified speech, with improvement in intelligibility for speech spoken in moderate background noise (66 and 72 dBSPL). The effect of the "buzz" of the artificial larynx is reduced, and speakers are better understood in moderate background noise with this amplification system.

Amplifiers, Electronic↗
PubMed1983

Amplification bandwidth and intelligibility of speech in quiet and noise for listeners with sensorineural hearing loss.

The intelligibility of speech mixed with noise (+6 dB S/N) and in quiet was measured as a function of its audible bandwidth for 7 listeners with moderate sensorineural hearing losses. Words were presented at three levels in the field (50, 60 and 70 dB SPL) and amplified with a Limiting Master Hearing Aid (LMHA) which allows independent control of gain and maximum power output in each of nine, half-octave channels. The frequency gain characteristics were chosen so the speech spectrum (60 dB SPL) at the input was shaped to approximate the individual listener's contour of most comfortable listening levels at the output. At each level and for the words in noise as well as quiet, the LMHA was set for four bandwidths (266-6 000, 375-4 242, 530-3 000 and 750-2 121 Hz). For these conditions, the listeners all obtained the highest mean score with the LMHA set for the widest bandwidth. The listener's ability to understand the words, after adjustment for individual differences, was well correlated (0.77-0.91) with the articulation index. Preliminary observations on the acceptability of amplified sounds, that is, loud speech, impact noise, an air-horn blast, and a party ratchet, are included.

Adult↗