[Aspects of voice quality quantification]. / Quantification des aspects qualitatifs de la voix.

The present work is directed towards providing a complement to the current use of sustained sounds as the basis for the physical measurement of voice quality parameters. For many clinical observations, there is a clear lack of correspondence between the measurement results, for example of shimmer, jitter and harmonic to noise ratio, and the perceived quality of the speaking voice. Our work is motivated by the need to overcome this familiar problem. It has four main objectives: to use running speech as the basis for one set of measurements in the clinical protocol; to link physical measures based on the use of this data with both production and perception; to employ voice production data as the foundation for auditorily significant criteria; the presentation of quantitative comparisons using sustained sound and running speech data, derived for a range of pathological voice conditions, within the same clinical session. Our pilot observations are based on the use of clinical acoustic and laryngographic data from patients of 4 different clinical centres.

Real-time speech pattern element displays for interactive therapy.

New developments are presented and discussed for the interactive display and separate measurement of frication and nasality in addition to voice quality. Different clinical problems require different therapeutic and quantitative approaches and these are ideally supported by appropriate combinations of speech pattern elements. Particular use has been made of the laryngograph signal in order to solve the problems of analysis and so that the displays can be given both a sense of immediacy and be highly accurate.

Laryngograph: speech pattern element tools for therapy, training and assessment.

The clinically based, real-time analysis of speech into physically definable elements, which are of direct perceptual and productive importance, has become more readily possible in recent years as the result of microprocessor developments. The combination of the acoustic signal of speech derived from a microphone together with the accompanying Laryngograph signal provides the basis for a highly reliable set of facilities. The paper describes methods and results for the analysis of voice, frication and timbre for both quantitative analysis and teaching and therapy using interactive visual displays. A brief discussion is given of links to work in stroboscopy, electropalatography and the associated use of additional sensors. Finally reference is made to a complete clinical work station combining these different facilities together with the quantitative analytical procedures of the speech pattern audiometer.

Speech pattern audiometry for clinical use.

A new PC-based speech perception testing system ('speech pattern audiometer') is described which aims to provide a simple and efficient clinical tool to assess patients' ability to make use of the acoustic speech pattern information which is fundamental to speech perception. The speech pattern audiometer is likely to find its main application in audiology and speech and language therapy clinics with those who are deaf or who have developmental or acquired speech-perceptual disorders. This system constitutes a module of a complete speech and hearing assessment and teaching/therapy workstation.

New developments in speech pattern element hearing aids for the profoundly deaf.

Two new developments in speech pattern processing hearing aids will be described. The first development is the use of compound speech pattern coding. Speech information which is invisible to the lipreader was encoded in terms of three acoustic speech factors; the voice fundamental frequency pattern, coded as a sinusoid, the presence of aperiodic excitation, coded as a low-frequency noise, and the wide-band amplitude envelope, coded by amplitude modulation of the sinusoid and noise signals. Each element of the compound stimulus was individually matched in frequency and intensity to the listener's receptive range. Audio-visual speech receptive assessments in five profoundly hearing-impaired listeners were performed to examine the contributions of adding voiceless and amplitude information to the voice fundamental frequency pattern, and to compare these codings to amplified speech. In both consonant recognition and connected discourse tracking (CDT), all five subjects showed an advantage from the addition of amplitude information to the fundamental frequency pattern. In consonant identification, all five subjects showed further improvements in performance when voiceless speech excitation was additionally encoded together with amplitude information, but this effect was not found in CDT. The addition of voiceless information to voice fundamental frequency information did not improve performance in the absence of amplitude information. Three of the subjects performed significantly better in at least one of the compound speech pattern conditions than with amplified speech, while the other two performed similarly with amplified speech and the best compound speech pattern condition. The three speech pattern elements encoded here may represent a near-optimal basis for an acoustic aid to lipreading for this group of listeners. The second development is the use of a trained multi-layer-perceptron (MLP) pattern classification algorithm as the basis for a robust real-time voice fundamental frequency extractor. This algorithm runs on a low-power digital signal processor which can be incorporated in a wearable hearing aid. Aided lipreading for speech in noise was assessed in the same five profoundly hearing-impaired listeners to compare the benefits of conventional hearing aids with those of an aid which provided MLP-based fundamental frequency information together with speech+noise amplitude information. The MLP-based pattern element aid gave significantly better performance in the reception of consonantal voicing contrasts from speech in pink noise than that achieved with conventional amplification and consequently, it also gave better overall performance in audio-visual consonant identification.(ABSTRACT TRUNCATED AT 400 WORDS)

Speech pattern hearing aids for the profoundly hearing impaired: speech perception and auditory abilities.

A family of prototype speech pattern hearing aids for the profoundly hearing impaired has been compared to amplification. These aids are designed to extract acoustic speech patterns that convey essential phonetic contrasts, and to match this information to residual receptive abilities. In the first study, the presentation of voice fundamental frequency information from a wearable SiVo (sinusoidal voice) aid was compared to amplification in 11 profoundly deafened adults. Intonation reception was often better, and never worse, with fundamental frequency information. Four subjects scored more highly in audio-visual consonant identification with fundamental frequency information, five performed better with amplified speech, and two performed similarly under these two conditions. Five of the 11 subjects continued use of the SiVo aid after the tests were complete. A second study examined a laboratory prototype compound speech pattern aid, which encoded voice fundamental frequency, amplitude envelope, and the presence of voiceless excitation. In five profoundly deafened adults, performance was better in consonant identification when additional speech patterns were present than with fundamental frequency alone; the main advantage was derived from amplitude information. In both consonant identification and connected discourse tracking, performance with appropriately matched compound speech pattern signals was better than with amplified speech in three subjects, and similar to performance with amplified speech in the other two. In nine subjects, frequency discrimination, gap detection, and frequency selectivity were measured, and were compared to speech receptive abilities with both amplification and fundamental frequency presentation. The subjects who showed the greatest advantage from fundamental frequency presentation showed the greatest average hearing losses, and the least degree of frequency selectivity. Compound speech pattern aids appear to be more effective for some profoundly hearing-impaired listeners than conventional amplifying aids, and may be a valuable alternative to cochlear implants.

Development of phonetic labeling in hearing-impaired children.

The development of labeling ability of an unselected group of 16 severely to profoundly hearing-impaired children was assessed over a period of 4 years, using synthetic speech pattern tests of increasing acoustic complexity. Detailed results are presented for six children matched in pairs in terms of their average pure-tone thresholds. All children showed progress in their ability to label at least some of the contrasts. Development was usually seen for the vowel contrast before the more complex initial consonant voicing contrast. Rate of development was not closely related to average pure-tone thresholds.

The effects of two different speech-coding strategies on voice fundamental frequency control in deafened adults.

Control of voice fundamental frequency (Fx) during reading of a standard passage was assessed for four profoundly deafened adults receiving auditory feedback in one of two conditions: (i) with an extended low-frequency response amplifying aid; (ii) with the SiVo aid, which provided only Fx information. A third condition, where the subjects were unaided, was also included. For each feedback condition, quantitative analyses of laryngograph recordings were used to provide measures of Fx mode, 90% Fx range and the regularity of vocal fold vibration. In baseline unaided recordings, three subjects (S1, S2 and S4) showed some aspects of Fx control outside the normal range, while the other (S3) had appropriate Fx control. In the three subjects with impaired control, simplified Fx feedback led to better control than feedback from amplified speech. In two of these subjects, these differences were statistically significant. S3, who showed unimpaired Fx control, did not show any changes in Fx control under the different feedback conditions. Although the patterns of data were different in the individual subjects, simplified Fx feedback led to either improved or unimpaired control of Fx relative to speech feedback or to not feedback. These findings have important implications for speech-processing strategies implemented in hearing aids and cochlear implants, where the effects of different speech-coding strategies on production have been largely ignored.

Psychoacoustic aspects of speech pattern coding for the deaf.

The SiVo aid, which provides a sinusoidal signal indicating voice fundamental frequency and voicing information, was compared as an aid to lipreading to a conventional hearing aid having extended low-frequency output. Speech perceptual measures of consonant confusions in lipreading and the identification of a simple intonation contrast were collected from a group of 8 profoundly deaf adults. Audiometric and psychoacoustic measures were also collected. In the intonation task, 6 of the 7 patients tested performed better with the SiVo aid and the seventh scored perfectly with both aids. Four patients (out of 8) preferred to use the SiVo aid rather than the conventional aid, and 2 of these showed a significant advantage with the SiVo aid in the aided lipreading of consonants. The remaining 4 patients preferred the conventional aid, although none of these patients showed a significant advantage with the conventional aid in the lipreading of consonants. The 4 patients who preferred the SiVo aid over the conventional aid had very profound hearing loss and minimal dynamic range at 500 Hz and above, and those receiving the greatest benefit showed no measurable frequency selectivity. In the 2 patients who preferred the SiVo aid, yet showed no significant advantage for the SiVo aid in consonant lipreading, consonant confusions were also measured for aided lipreading, using a prototype aid providing both voice fundamental frequency and voiceless excitation patterns. Both patients showed additional and significant benefit from inclusion of the voiceless pattern element.

Prospects for speech pattern element aids.

A brief discussion is given of new hearing aids which are based on the use of speech pattern elements. Their operation essentially involves the reduction of the complex acoustic structure of the original speech signal into simpler sets of perceptually clear components which are then encoded for maximally relevant presentation to the listener. This approach has four primary features which may contribute crucially to future advances. First, by providing for external analysis, reduced or even non-existent ability in the impaired ear can be palliated. Second, by the selection of appropriate elements of the original speech signal, the stimulation can be tailored so that it matches the residual auditory ability--psychophysical and cognitive--of the deaf person. Third, the speech, language, and also environmental needs of the individual adult or developing child can be met in structured ways. Fourth, the use of selective pattern sensitive analysis methods makes it possible in practice to provide a degree of in-built immunity to domestic and working acoustic environments.

The development of contrastiveness in profoundly deaf children's speech.

This paper presents some of the results from a study of certain perceptual and productive characteristics of the speech of a group of 16 severely-profoundly deaf children over a period of 4 years who formed a complete class in an oral school. The extent to which they follow a normal pattern of development is discussed.

Structural effects of short term and chronic extracochlear electrical stimulation on the guinea pig spiral organ.

To assess the effects of extracochlear electrical stimulation on cochlear structure, guinea pigs were implanted and stimulated with single middle ear electrodes either at round window or promontory sites, and their cochleae examined by transmission electron microscopy. Implanted but unstimulated, or unimplanted control animals were examined in the same way. Alternating current stimulation at the promontory for 2 h at 150 Hz, 500 microA, caused outer hair cell efferent endings to become dense and vacuolated, but no hair cells were damaged. With direct current stimulation at 500 microA for 2 h the basal regions of the stimulated cochlea were badly damaged and many outer hair cells lysed. Long term (up to 1200 h) round window stimulation at 100 or 141 Hz, 15-91 microA rms, did not cause cell death or inner hair cell damage, but basal outer hair cells and their efferent endings were badly affected in both ipsilateral and contralateral cochleae. The compound action potential of the auditory evoked response to broad band click stimuli was not altered by chronic electrical stimulation. It is concluded that chronic stimulation with the parameters used does not threaten cochlear survival, and it is proposed that the bilateral structural changes induced by chronic stimulation are caused by excessive activation of the cochlear efferent pathways.

A microprocessor-based acoustic hearing aid for the profoundly impaired listener.

We have found that the larynx-frequency pattern of speech presented as a sinusoid can be of greater communicative value to profoundly hearing-impaired people than the complete acoustic signal. The presence of higher harmonics can give poorer labelling of isolated intonation contrasts and often minimal gain in segmental spectrally-based distinctions. These observations have led to the development of a practical, body-worn, pattern-processing hearing aid that uses a microprocessor to sense the (analogue-processed) speech fundamental frequency, transform it into an appropriate amplitude and frequency region, and generate digitally the required output sinusoid. Our findings have important implications for the design of other signal-processing hearing aids in demonstrating that a simplification of speech can lead to enhanced speech receptive abilities in persons with impaired hearing.

Structural alteration of hair cells in the contralateral ear resulting from extracochlear electrical stimulation.

Chronic electrical stimulation of the auditory nerve in patients with profound sensori-neural deafness is becoming increasingly routine. Therefore, it is important to understand more about the long-term consequences of this procedure. Hitherto, structural studies in animals after electrocochlear stimulation have concentrated on the stimulated cochlea. Here we have examined the effects of unilateral extracochlear electrical stimulation on the spiral organ of both the ipsilateral and contralateral ears of the mature guinea pig, and have found alterations in the structure of the outer hair cells and their efferent nerve terminals in the contralateral as well as the ipsilateral cochlea. This is the first evidence for a structural influence of efferent activity on the cochlea. Although the importance of the efferent system, consisting of the crossed and uncrossed olivo-cochlear bundles, is well established in providing central control of the sensory pathways, its exact role in hearing is incompletely understood. However, it is known that the outer hair cells and their efferent innervation are important in their contribution to inner hair cell responses and in modulating the micromechanics of the whole cochlea. These efferent functions now appear to be related to an important part of cochlear morphology, and are also relevant to our understanding of cochlear neurobiology, normal development and the management of hearing disability in both adult and child.

Audiological rehabilitation of patients with brainstem disorders.

A brief account is given of the course of rehabilitation of three patients with severe brainstem injuries. Particular use has been made of synthetic speech pattern assessment procedures which have been integrated into the management model of Goldstein and Stephens (1981). The use of speech stimuli of controllable simplicity has two main clinical benefits: the early course of re-acquisition can be examined analytically, second, aspects of speech receptive and productive rehabilitation can be facilitated. Re-acquisition of perceptive ability in some of these patients may follow a progression from simple to complex acoustic pattern contrasts and this may provide an effective basis for future techniques of rehabilitation.

Microprocessor-controlled speech pattern audiometry. Preliminary results.

Interactive microprocessor-controlled speech pattern tests making use of high-quality synthetic speech have been used to assess the development of subjects' ability to process speech contrasts of increasing complexity, from prosodic contrasts to a 'date-gate' place contrast. These tests have been particularly useful in mapping the development or recovery of subjects functioning at the very first stages of processing ability. Some results obtained with profoundly hearing-impaired children and with adults suffering from brain stem disorders are reported, and further applications of speech pattern audiometric techniques are briefly discussed.

Speech pattern element stimulation in electrical hearing.

A sensation of hearing is provided for the otherwise totally deaf adult by the use of an electrode arrangement, placed external to the cochlea, which provides only larynx frequency speech pattern information. This is normally obtained by acoustic analysis and is presented so that, although its pattern is preserved, its physical form is matched to the patient's auditory capacity. Speech-receptive improvement has been shown using interactive synthetic speech techniques, video-recorded lipreading tests, and interactive conversational-type presentations. Speech production skills are also enhanced by self-monitoring, and examples of voice range improvement and jitter reduction are given. The particular electrode system used is especially suitable for promontory stimulation in adult patients without a tympanic membrane. The work as a whole is relevant, however, to the design of other conservative prostheses for both deaf adults and children.

Clinical analysis of laryngeal trauma secondary to intubation.

A study was undertaken to analyse the effect of short-term intubation on the voice. Children were examined laryngographically both pre- and postoperatively. Changes in larynx frequency distribution following intubation were documented using the technique of electrolaryngography; the resolution of these changes was similarly recorded. The results, in comparison with the frequency distributions associated with other disease states, give insight into the nature of the damage and its effect on vocal fold vibratory patterns. The technique therefore enables objective evidence of minor degrees of laryngeal trauma to be demonstrated and differentiated.

Speech signal presentation to the totally deaf.

We have developed a system for single-channel electrical stimulation of the totally deaf. The patient wears a removeable electrode assembly which stimulates the cochlear promontory and can be inserted and removed like the earmould of a hearing aid. This approach minimises the risk of mechanical or electro-chemical damage to structures within the cochlea. Charge-balanced stimulation is used to present those speech pattern elements that are matched to the patients' lipreading needs and their new sensory abilities. Objective tests show improvements both in patients' perceptive and productive abilities.

Examination of vocal fold movement by ultra-short pulse X radiography.

Antero-posterior radiographs of the larynx lack spatial and temporal resolution, due to the movement of the vocal folds during phonation. By utilising the electrolaryngograph to monitor vocal fold movement, single X-ray pulses of 30 nanoseconds duration have been triggered at pre-determined points during the cycle of vocal fold movement to visualise these in normal phonation.