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Effect of visual cuing on synthetic speech intelligibility: a comparison of native and nonnative speakers of English.

This study compared the effect of visual cuing on the intelligibility of DECtalk for native and nonnative speakers of English in both ideal listening conditions and in the presence of background noise at a signal to noise (S/N) ratio of + 10dB. Visual cuing improved DECtalk's intelligibility for nonnative speakers more than for native speakers, especially in the background noise condition. Implications of these findings and the need for further research are discussed.

Adult↗

Effects of subthalamic nucleus stimulation on parkinsonian dysarthria and speech intelligibility.

Subthalamic stimulation is known to improve tremor, akinesia and rigidity in Parkinson's disease. However, other signs such as hypophonia and swallowing disorders can be relatively resistant to this technique. The effect on dysarthria remains unclear. The aim of this study was to investigate the effects of implantation of electrode and stimulation of the subthalamic nucleus (STN) on parkinsonian dysarthria. Seven patients were prospectively included. Electrodes (Medtronic) were implanted in both STN. The electrode contacts and stimulation parameters were adjusted to provide best relief of symptoms with fewest side effects. Assessment used global scales (Unified Parkinson Disease Rating Scale, UPDRS II and III), dyskinesia scale, exhaustive dysarthria assessment (bucco-facial movements, voice, articulation, intelligibility) and the 'dysarthria' item from the UPDRS III. Evaluations were performed in six conditions: before and three months after surgery (pre-op, post-op) stimulation turned off or on (off-stim, onstim), and without or with a suprathreshold levodopa dose (offdrug, on-drug). Performance level on the UPDRS III significantly improved following electrode implantation and stimulation. For dysarthria, modest beneficial effects were observed on several motor parameters, especially lip movements. Voice mildly improved, especially for the modulation in loudness and pitch. Articulation was not affected. Furthermore, intelligibility was slightly reduced in the on-stimulation condition, especially when patients received levodopa. At an individual level, negative effects on intelligibility were observed in two patients, and this was associated with a discrete increase in facial and trunk dyskinesias, but not with the electrode position or stimulation parameters. In conclusion, surgery had weak effects on dysarthria. Intelligibility can be worsened, especially in the on-drug condition. Thus, adaptation of the stimulation parameters can be difficult.

Aged↗

Speech intelligibility of two voice output communication aids.

The purpose of the study was to investigate the intelligibility of two voice output communication aids. Twenty words and 20 sentences, synthesized with the Personal Communicator and with the SpeechPAC, were presented to 20 listeners. Listener transcriptions of the stimuli were used to compare the intelligibility of the two communication aids. Analysis of variance revealed significantly higher intelligibility scores for the Personal Communicator compared to the SpeechPAC and higher scores for sentences than for words. The implications of these findings for selection of augmentative communication devices is discussed.

Adult↗

The prediction of speech intelligibility in underground stations of rectangular cross section.

Long enclosures are spaces with nondiffuse sound fields, for which the classical theory of acoustics is not appropriate. Thus, the modeling of the sound field in a long enclosure is very different from the prediction of the behavior of sound in a diffuse space. Ray-tracing computer models have been developed for the prediction of the sound field in long enclosures, with particular reference to spaces such as underground stations which are generally long spaces of rectangular or curved cross section. This paper describes the development of a model for use in underground stations of rectangular cross section. The model predicts the sound-pressure level, early decay time, clarity index, and definition at receiver points along the enclosure. The model also calculates the value of the speech transmission index at individual points. Measurements of all parameters have been made in a station of rectangular cross section, and compared with the predicted values. The predictions of all parameters show good agreement with measurements at all frequencies, particularly in the far field of the sound source, and the trends in the behavior of the parameters along the enclosure have been correctly predicted.

Confined Spaces↗

Comparison of calculated, measured and self-assessed intelligibility of speech in noise for hearing-aid users.

The Speech Intelligibility Index (SII) was used along with paired-comparison judgements and speech recognition scores to compare the speech intelligibility provided by two hearing-aid frequency responses in two different background noises. The purpose was to validate an SII-based procedure. Test subjects were 26 hearing-aid users representing a wide range of hearing loss configurations. One hearing-aid setting was in close agreement with the NAL-R prescription, whereas the other setting was achieved by reducing the high-frequency gain by about 10 dB compared to NAL-R. There were good overall agreements between results of the three methods. Average speech recognition scores were about 4 percentage points higher for the NAL-R frequency response, which also was subjectively judged as significantly better in terms of speech intelligibility. The SII based procedure was found to be suitable for comparing hearing-aid characteristics within subjects.

Aged↗

Influence of the speaker and other factors affecting speech intelligibility.

20 phonetically balanced word lists comprising 25 words in each and recorded on tape by a professional announcer have been tested on 45 subjects. Analysis of the results has enabled each of the 500 words to be assigned a grade of difficulty within the range 1-35. 25 'difficult' and 25 'easy' words re-recorded from the original tapes to form two new lists have been shown to retain their same grade of difficulty. With the same lists recorded by two additional speakers, however, word order difficulty was dramatically altered. Consideration has been given to various factors likely to affect word intelligibility including phonetic construction, word familiarity and word environment. None appeared to exert any marked influence. It is concluded that the characteristics of any recorded word articulation material are determined predominantly by the speaker and the recording technique adopted and are largely independent of other factors. Given sufficient experimental data upon recorded material, words can be selected out of context and re-recorded to provide test lists with virtually any desired characteristics.

Audiometry, Speech↗

Effects of auditory fatigue on speech intelligibility and lexical decision in noise.

The influence of weak auditory fatigue on speech identification and lexical decision (word/nonword) was studied. It appears that, at a low listening level and in presence of a strong masking noise, auditory fatigue gives rise to: (1) a decrease in identification scores, (2) more frequent confusions for fricatives, (3) a reduction in correct lexical decision scores, (4) an increase in the tendency to respond "word" more often than "nonword" (5) a slight increase in reaction times for incorrectly repeated items. The intelligibility impairment can be attributed to a combination of masking and fatigue effects. Errors in lexical decisions and changes in response times are explained by an adaptation of the lexical decision processes to the degraded perceptual representations of the stimuli. There is no clear evidence in this experiment that a very central component of auditory fatigue influences lexical decisions.

Adult↗

Changes in speech intelligibility of postlingually deaf adults after cochlear implantation.

OBJECTIVE: This study examines changes in the intelligibility of CVC words spoken by postlingually deafened adults after they have had 6 to 12 mo of experience with a cochlear implant. The hypothesis guiding the research is that the intelligibility of these speakers will improve after extended use of a cochlear implant. The paper also describes changes in CVC word intelligibility analyzed by phoneme class and by features. DESIGN: The speech of eight postlingually deaf adults was recorded before activation of the speech processors of their cochlear implants and at 6 mo and 1 yr after activation. Seventeen listeners with no known impairment of hearing completed a word identification task while listening to each implant user's speech in noise. The percent information transmitted by the speakers in their pre- and postactivation recordings was measured for 11 English consonants and eight vowels separately. RESULTS: An overall improvement in word intelligibility was observed: seven of the eight speakers showed improvement in vowel intelligibility and six speakers showed improvement in consonant intelligibility. However, the intelligibility of specific consonant and vowel features varied greatly across speakers. CONCLUSIONS: Extended use of a cochlear implant by postlingually deafened adults tends to enhance their intelligibility.

Aged↗

Changes in aesthetic appearance and intelligibility of speech after partial glossectomy in patients with Down syndrome.

Eight patients with Down syndrome, aged 9 years and 10 months to 25 years and 4 months, underwent partial glossectomy. Preoperative and postoperative videotaped samples of spoken words and connected speech were randomized and rated by two groups of listeners, only one of which knew of the surgery. Aesthetic appearance of speech or visual acceptability of the patient while speaking was judged from visual information only. Judgments of speech intelligibility were made from the auditory portion of the videotapes. Acceptability and intelligibility also were judged together during audiovisual presentation. Statistical analysis revealed that speech was significantly more acceptable aesthetically after surgery. No significant difference was found in speech intelligibility preoperatively and postoperatively. Ratings did not differ significantly depending on whether the rater knew of the surgery. Analysis of results obtained in various presentation modes revealed that the aesthetics of speech did not significantly affect judgment of intelligibility. Conversely, speech acceptability was greater in the presence of higher levels of intelligibility.

Adolescent↗

Effects of reverberation and masking on speech intelligibility in cochlear implant simulations.

Two experiments investigated the impact of reverberation and masking on speech understanding using cochlear implant (CI) simulations. Experiment 1 tested sentence recognition in quiet. Stimuli were processed with reverberation simulation (T=0.425, 0.266, 0.152, and 0.0 s) and then either processed with vocoding (6, 12, or 24 channels) or were subjected to no further processing. Reverberation alone had only a small impact on perception when as few as 12 channels of information were available. However, when the processing was limited to 6 channels, perception was extremely vulnerable to the effects of reverberation. In experiment 2, subjects listened to reverberated sentences, through 6- and 12-channel processors, in the presence of either speech-spectrum noise (SSN) or two-talker babble (TTB) at various target-to-masker ratios. The combined impact of reverberation and masking was profound, although there was no interaction between the two effects. This differs from results obtained in subjects listening to unprocessed speech where interactions between reverberation and masking have been shown to exist. A speech transmission index (STI) analysis indicated a reasonably good prediction of speech recognition performance. Unlike previous investigations, the SSN and TTB maskers produced equivalent results, raising questions about the role of informational masking in CI processed speech.

Acoustics↗

Speech intelligibility through communication headsets for general aviation.

Word discrimination was measured on eight general aviation pilots listening alternately through each of three communication headsets and an aircraft loudspeaker in the presence of light aircraft noise. Each subject listened at the speech intensity designated by him as yielding optimal intelligibility. Performance varied directly with the degree of attenuation provided by the headset. Mean intelligibility scores ranged from 73% through the loudspeaker to 92% through two of the headsets, although retesting through the loudspeaker at a higher signal level improved mean scores to 85%. Articulation functions obtained on four normally hearing listeners tested under the same conditions as the pilots revealed that, for situations when little or no attenuation was available (loudspeaker and one headset), greater signal-to-noise ratios were necessary to allow discrimination equivalent to that obtained under conditions of greater noise attenuation (two headsets). Although good intelligibility could be achieved through the loudspeaker given sufficient signal intensity (greater than 100 dB SPL) some pilots preferred lower levels even though discrimination was reduced.

Aerospace Medicine↗