Production of intonation and contrastive stress in electrolaryngeal speech

Acoustical investigations of intonation and contrastive stress patterns in speech produced with electronic artificial larynges were completed. High-quality tape recordings of sentences spoken by 4 normal speakers, 3 users of the Western Electric 5A electrolarynx, and 2 users of the Servox electrolarynx were subjected to acoustic analysis. All electrolarynx users distinguished stressed from unstressed syllables by varying the duration of syllables and contiguous pauses. One Western Electric 5A speaker also controlled fundamental frequency. This speaker distinguished statements from questions by varying the rate and extent of the initial rising portion of fundamental frequency contours. Findings are interpreted in relation to their implications for clinical intervention and in terms of suggestions for improved design of artificial larynges.     

Comparison of ratings of four artificial larynges

Fifty-six tape-recorded readings of the “Rainbow Passage” were played to 29 naive listeners for judgments regarding acceptability of artificial larynx speech. Both intraoral and neck-type devices were used, with comparisons among brands of particular interest. The Cooper-Rand, orally adapted Servox, AT&T 5 C, and the neck Servox were used in eliciting speech samples from 14 male esophageal speakers. Listeners rated acceptability using a seven-point equal-appearing interval scale. All devices were rated similar in fluency acceptability, inflection, and overall communicative effectiveness. Speaking rates were judged more acceptable with the oral Servox and least acceptable with the Cooper-Rand. Pitch/quality was more acceptable with intraoral devices than with neck devices, with the oral Servox rated highest. Clinical implications regarding the perceptual findings are discussed, with information about specific brands provided for patient counseling.     

Tongue strength: Part II: In artificial alaryngeal speech

Tongue strength does not appear to be reduced in proficient esophageal speakers. However, no data exist on tongue strength for laryngectomized subjects who have not developed esophageal speech. Anterior and lateral tongue strength measures were obtained from 13 laryngectomized subjects who used an artificial larynx and 15 normal subjects by means of a pressure transducer and recording device. The results indicated that laryngectomized subjects had significantly weaker tongues in two of three directions measured. It was concluded that laryngectomy may affect tongue strength, but that the method of alaryngeal speech utilized postoperatively influences the return to normal.     

Acoustical analysis of Spanish vowels produced by laryngectomized subjects.

The purpose of this study was to describe the acoustic characteristics of Spanish vowels in subjects who had undergone a total laryngectomy and to compare the results with those obtained in a control group of subjects who spoke normally. Our results are discussed in relation to those obtained in previous studies with English-speaking laryngectomized patients. The comparison between English and Spanish, which diFfer widely in the size of their vowel inventories, will help us to determine specific or universal vowel production characteristics in these patients. Our second objective was to relate the acoustic properties of these vowels to the perceptual data obtained in our previous work (J. L. Miralles & T. Cervera, 1995). In that study, results indicated that vowels produced by alaryngeal speakers were well perceived in word context. Vowels were produced in CVCV word context by two groups of patients who had undergone laryngectomy: tracheoesophageal speakers (TES) and esophageal speakers. In addition a control group of normal talkers was included. Audio recordings of 24 Spanish words produced by each speaker were analyzed using CSL (Kay Elemetrics). Results showed that F1, F2, and vowel duration of alaryngeal speakers differ significantly from normal values. In general, laryngectomized patients produce vowels with higher formant frequencies and longer durations than the group of laryngeal subjects. Thus, the data indicate modifications either in the frequency or temporal domain, following the same tendency found in previous studies with English-speaking laryngectomized speakers.     

The Lombard effect on alaryngeal speech

The need to train alaryngeal speakers to use increased vocal intensity has been noted in the literature. One untested technique is to evoke an intensity increase by applying masking noise to the ears of the talker. The purpose of this study was to investigate the Lombard effect on the speech of esophageal talkers, artificial larynx users, and normal speakers. The subjects read aloud a variety of materials first in quiet then while being subjected to 100 dB SPL noise delivered through earphones. The resulting sound pressure values were obtained by measuring the peak values of all syllables spoken by each talker. The results indicated that the esophageal talkers produced the highest intensity increase in the noise condition followed by the normal talkers and the artificial larynx talkers. Coarticulatory and duration effects on alaryngeal and normal speech are also reported. Clinical implications are discussed.     

Spectral slope of vowels produced by tracheoesophageal speakers

Spectra of vowels were analyzed to determine whether differences exist between the spectral slope of vowels produced by tracheoesophageal (TE) speakers and normal speakers and, if so, to quantify such differences. The linear predictive autocorrelation method was used to calculate smoothed spectra and the spectra were normalized with respect to a low frequency component. Comparisons between normalized spectral energy within a selected high frequency range revealed that energy within this frequency range for vowels produced by TE speakers was significantly higher than that produced by normal speakers. A least-square distance matching procedure was used to quantify speaker group differences in the spectral slope of vowels. Average spectra of vowels produced by the normal speakers could be matched to average spectra of vowels produced by the TE speakers by decreasing the spectral slope of their vowels by 2-3 dB/octave.     

Voice onset time in Thai alaryngeal speech

The perception and production of voicing contrast was investigated in utterances spoken by Thai alaryngeal speakers. Thai exhibits a three-category voicing distinction for bilabial /b, p, ph/ and alveolar /d, t, th/ stops and a two-category distinction for velar [k, kh] stops. Voice onset time (VOT) was measured in word-initial stops of words produced in isolation by 2 Thai esophageal speakers and 1 Thai user of an electronic artificial larynx. These measurements were compared with published VOT values for the same words spoken by 5 normal Thai speakers. Both esophageal speakers were capable of signaling voicing distinctions for /b, d/ and /p, t, k/. The electrolaryngeal speaker was able to signal /p, t, k/ only. Thai alaryngeal speakers were generally unsuccessful in signaling /ph, th, kh/. A cross-linguistic comparison to VOT in English suggests that no more than two voicing categories can be distinguished in these two forms of alaryngeal speech. Findings are interpreted to illustrate that the realization of stop voicing contrasts in alaryngeal speech depends on the number of voicing categories in a language, the relative positions of the voicing categories on the VOT continuum, and the form of alaryngeal speech.     

Tongue strength: Part I: Following total laryngectomy

Surgical repositioning of the genioglossus muscle, as in total laryngectomy, may have an adverse effect on the protrusive strength of the tongue. To test this premise, anterior and lateral tongue strength measures were obtaind from 10 laryngectomized and 15 normal subjects by means of a pressure transducer and recording device. The results indicated no significant difference between laryngectomized and normal subjects on tongue strength measures. Further, all laryngectomized subjects were judged to have good to excellent esophageal speech. It was concluded that laryngectomy does not adversely affect the major musculature concerned with protrusive tongue strength for proficient esophageal speakers.     

Perception of pitch contours in single words in alaryngeal speech.

The perception and production of pitch contours were investigated in single words produced by two groups of alaryngeal speakers: tracheo-oesophageal (TE) and oesophageal (E) speakers. High quality tape-recordings of three tonal patterns by four oesophageal and eight tracheo-oesophageal speakers in monosyllabic words were judged by a group of six speech and language therapy listeners. The results indicated that tonal patterns can be produced with a relatively high level of reliability for both speaker groups. Some individual speakers from both groups approached predicted normal levels. These findings emphasise the importance of providing the opportunity for patients to acquire either of these speech modes in alaryngeal rehabilitation, rather than simply being provided with an artificial larynx, particularly in countries where tone languages are used. The high variability between groups also suggests that other variables apart from alaryngeal speech mode may be relevant in determining ability to signal tonal patterns.     

Improving alaryngeal speech intelligibility

Laryngectomized patients using esophageal speech or an electronic artificial larynx have difficulty producing correct voicing contrasts between homorganic consonants. Voicing of a voiceless consonant is the most frequent listener misidentification. A therapy technique is described that emphasizes “pushing harder” on voiceless consonants to improve the intelligibility of alaryngeal speakers. Laryngectomy speech therapy programs should focus first on the production of voiceless consonants before attempting to effect voicing.     

Acoustic and perceptual characteristics of vowels produced during simultaneous communication

This study investigated the acoustical and perceptual characteristics of vowels in speech produced during simultaneous communication (SC). Twelve normal hearing, experienced sign language users were recorded under SC and speech alone (SA) conditions speaking a set of sentences containing monosyllabic words designed for measurement of vowel duration, formant frequencies, and fundamental frequency in consonant-vowel-consonant (CVC) syllables and 60 listeners audited the speech samples. Although results indicated longer sentence and vowel durations for SC than SA, the data showed no difference in spectral characteristics of vowels produced during SC versus SA, indicating no degradation of vowel spectrum by rate alteration during SC. Further, no difference was found in listeners' ability to identify vowels produced during SC versus SA, indicating no degradation of vowel perceptual cues during SC. These conclusions are consistent with previous research indicating that temporal alterations produced by SC do not produce degradation of segmental acoustical characteristics of spoken English. LEARNING OUTCOMES: As a result of this activity, the participant will be able to (1) describe simultaneous communication; (2) explain the role of simultaneous communication in communication with children who are deaf; (3) describe vowel acoustics in English speech; (4) discuss methods of measuring vowel perception; (5) specify the acoustic characteristics of vowels produced during simultaneous communication; and (6) specify the ability of listeners to perceive vowels in speech produced during simultaneous communication.     

The effect of phonological neighborhood density on vowel articulation.

Recent literature suggests that phonological neighborhood density and word frequency can affect speech production, in addition to the well-documented effects that they have on speech perception. This article describes 2 experiments that examined how phonological neighborhood density influences the durations and formant frequencies of adults' productions of vowels in real words. In Experiment 1, 10 normal speakers produced words that covaried in phonological neighborhood density and word frequency. Infrequent words with many phonological neighbors were produced with shorter durations and more expanded vowel spaces than frequent words with few phonological neighbors. Results of this experiment confirmed that this effect was not related to the duration of the vowels constituting the high- and low-density words. In Experiment 2, 15 adults produced words that varied in both word frequency and neighborhood density. Neighborhood density affected vowel articulation in both high- and low-frequency words. Moreover, frequent words were produced with more contracted vowel spaces than infrequent words. There was no interaction between these factors, and the vowel duration did not vary as a function of neighborhood density. Taken together, the results suggest that neighborhood density affects vowel production independent of word frequency and vowel duration.     

Language-specific, hearing-related changes in vowel spaces: a preliminary study of English- and Spanish-speaking cochlear implant users.

OBJECTIVE: This study investigates the role of hearing in vowel productions of postlingually deafened cochlear implant users. Two hypotheses are tested that derive from the view that vowel production is influenced by competing demands of intelligibility for the listener and least effort in the speaker: 1) Hearing enables a cochlear implant user to produce vowels distinctly from one another; without hearing, the speaker may give more weight to economy of effort, leading to reduced vowel separation. 2) Speakers may need to produce vowels more distinctly from one another in a language with a relatively "crowded" vowel space, such as American English, than in a language with relatively few vowels, such as Spanish. Thus, when switching between hearing and non-hearing states, English speakers may show a tradeoff between vowel distinctiveness and least effort, whereas Spanish speakers may not. DESIGN: To test the prediction that there will be a reduction of average vowel spacing (AVS) (average intervowel distance in the F1-F2 plane) with interrupted hearing for English-speaking cochlear implant users, but no systematic change in AVS for Spanish cochlear implant users, vowel productions of seven English-speaking and seven Spanish-speaking cochlear implant users, who had been using their implants for at least 1 yr, were recorded when their implant speech processors were turned off and on several times in two sessions. RESULTS: AVS was consistently larger for the English speakers with hearing than without hearing. The magnitude and direction of AVS change was more variable for the Spanish speakers, both within and between subjects. CONCLUSION: Vowel distinctiveness was enhanced with the provision of some hearing in the language group with a more crowded vowel space but not in the language group with fewer vowels. The view that speakers seek to minimize effort while maintaining the distinctiveness of acoustic goals receives some support.     

Intelligibility characteristics of superior esophageal speech presented under various levels of masking noise.

Broad-band masking of speech was used to assess the effects that broad-band masking noise had upon the recognition of consonants and vowels produced by esophageal speakers. Procedures were developed to compare the articulation functions of superior esophageal speech with those of normal speech under comparable levels of masking noise. Within the range of speech-to-noise ratios studied, articulation functions for vowels were essentially the same for esophageal and normal talkers (4% per dB). With respect to consonants, the intelligibility scores for esophageal speech were 12 to 14% lower than for normal speech under adverse noise conditions. Gains in the consonant articulation functions were 2.5%/dB and 4%/dB for normal and esophageal talkers, respectively. For adverse noise conditions, the lowered consonant scores for esophageal speakers were the result of poorer than normal intelligibility for liquid-glides and nasal and, secondarily, for stop consonants. Additional differences between the intelligibility characteristics of esophageal and normal speech were found in work-position and voicing features.     

Eureka-project: ‘totally implantable artificial larynx’: progress report

Objective. The European Eureka project ‘Artificial larynx’ aims at realizing an implantable artificial larynx, consisting of artificial vocal folds, artificial epiglottis, tissue connector for tracheal fixation and valve mechanism to switch between breathing and speaking. The last part has been realized. Because its functioning is identical to a tracheostomal valve, it was tested as such. Materials and methods. The device consists of two valves: a speech valve, that will be open during normal breathing and closed by strong expiration and a cough valve that opens during coughing and closes automatically during inhalation. Magnets keep the valves in the breathing position. The magnetic force can be varied. Several prototypes have been tested in vitro and in situ. Results. The prototypes showed good in vitro behaviour. The range of adjustability of speech and cough was wide enough, flow resistance acceptable. This was confirmed by preliminary in vivo experiments. Patients were enthusiastic; hands-free speaking and coughing is possible. Conclusion. Numerous problems have to be solved to produce an artificial larynx. Each solution generated up till now, however, can already be applied to improve the existing rehabilitation process of laryngectomized patients.     

Acoustic differences between content and function words in amyotrophic lateral sclerosis.

Studies describing acoustic characteristics of speech produced by individuals with dysarthria may help to explain intelligibility deficits for these speakers. One goal of the current study was to investigate the manner and extent to which nine speakers with mild to moderate dysarthria associated with amyotrophic lateral sclerosis (ALS) and nine healthy speakers acoustically distinguished /i/, /ae/, /u/, and /a/ in content and function words. A further aim was to evaluate the relationship between impaired speech in ALS and the magnitude of acoustic differences for vowels in content and function words. Speakers read the Farm Passage at a comfortable or habitual rate. F1 and F2 midpoint frequencies were measured, and vowel space areas were calculated. Vowel durations also were measured. The magnitude of F1, F2, vowel space area, and duration differences for vowels in content and function words was not statistically different for speakers with ALS and healthy controls. In addition, with the exception of /i/ produced by some speakers with ALS, vowel duration tended to be shorter in function words. Average F1 and F2 values for function words also tended to be centralized relative to content words. Although vowel space area differences for the two speaker groups were not statistically significant, there was a tendency for the difference in vowel space area for content and function words to be smaller for speakers with ALS than for controls. Regression analyses further indicated that the magnitude of temporal differences for vowels in content and function words was a better predictor of impaired speech than the magnitude of spectral differences for vowels in content and function words. One clinical implication is that individuals with ALS may benefit from therapy techniques targeting temporal properties of the acoustic signal.     

An acoustic and perceptual study of final stops produced by profoundly hearing impaired adolescents.

PURPOSE: This study investigated formant frequencies for their role as acoustic and perceptual correlates to the place of articulation of Cantonese final stops produced by profoundly hearing impaired speakers. METHOD: Speakers were 10 Cantonese adolescents (mean age=13;5 [years;months]) who were profoundly hearing impaired (HI). Control speakers were 10 adolescents (mean age=13;5) with normal hearing. Stimuli were Cantonese words that were minimally contrastive in place of final stops (/p, t, k/). Listeners were 10 final-year speech therapy students. The frequencies of F1, F2, and F3 were measured at the middle, 40 ms before the end, and at the end of the vocalic segments. RESULTS: Control speakers distinguished place contrasts through formant frequency differences at the end positions of the vowels. HI speakers produced final stops with missing formant transitions and neutralized vowels preceding final stops. Listeners relied on F2 transition cues for stops produced by control speakers, whereas F1 and F3 transition cues were used for stops produced by HI speakers. CONCLUSIONS: Formant frequencies of final stops produced by HI speakers showed reduced place distinction. When listeners identified the place of final stops produced by HI speakers, they relied on formant frequency cues that were different from those used for stops produced by control speakers.     

Vertical laryngeal position during continuous and discrete vocal frequency change.

Six young adult male subjects produced sustained phonation throughout their vocal frequency ranges: first, in a glissando or continuous frequency change maneuver, and second, in discrete intervals at separate trials. Measures of intrinsic and extrinsic laryngeal muscle activity and vertical laryngeal position were related to voice fundamental frequency in the two conditions. Each subject consistently positioned his larynx at a resting level when he was instructed to relax or when he was not performing experimental tasks. All larynx positions during experimental tasks were measured as deviations from this resting level. Subjects showed a close correspondence between their vertical laryngeal positions and voice frequencies--more so for the glissando maneuver than for changes in discrete frequency tasks. In general, subjects lowered their larynges from the resting position for low-frequency phonation and raised their larynges for higher fundamental frequencies. Absolute larynx position for the same frequency was quite varied both within and between subjects. Vertical laryngeal position during phonation most often was directly related to the activity of the thyrohyoid and sternothyroid muscles. Neither vertical laryngeal movement nor intrinsic laryngeal activity showed any pattern of relationship to changes between modal and falsetto voice registers.     

Auditory-perceptual scaling and quality of life in tracheoesophageal speakers

Objectives/Hypothesis The purposes of the study were to determine listeners' auditory‐perceptual ratings of tracheoesophageal speakers, to determine quality of life in tracheoesophageal speakers, and to determine the potential relationship between listeners' ratings of speech and tracheoesophageal speakers' self‐rated quality of life. Study Design Twenty‐eight laryngectomized individuals who used tracheoesophageal speech as their primary mode of communication were studied. Fifteen naïve listeners provided auditory‐perceptual ratings. Methods Twenty‐eight tracheoesophageal speakers (22 men and 6 women) completed a general information form, in addition to the University of Michigan Head and Neck Quality of Life (HNQOL) instrument; speakers also provided connected speech samples of a standard passage. Fifteen naïve listeners evaluated the tracheoesophageal speech samples for overall speech severity, naturalness, acceptability, and pleasantness using direct magnitude estimation procedures. Results Listeners were able to discriminate among tracheoesophageal speech samples relative to the auditory‐perceptual dimensions. Male tracheoesophageal speakers were judged as having significantly better, more acceptable, and more pleasant voices than women. Scores on the HNQOL instrument were determined to be higher among the group of tracheoesophageal speakers in the present study than those reported in previous studies. No significant differences were found among men and women for quality of life scores. Quality of life domains and auditory‐perceptual judgments of tracheoesophageal speech were moderately correlated. Conclusion Women who use tracheoesophageal speech may be differentially penalized for dimensions related to voice quality. Limitations in voice did not necessarily translate into worse overall quality of life, indicating that auditory‐perceptual evaluation and quality of life questionnaires are evaluating different aspects of function after laryngectomy.