Acoustic and perceptual study of Cantonese tones produced by profoundly hearing-impaired adolescents

OBJECTIVE: This study investigated five acoustic parameters of fundamental frequency (f0), one related to average f0 level and four related to change of f0 (f0 change) over four consecutive quarters of the vocalic segment, for their roles as acoustic correlates to the perception of Cantonese lexical tones produced by profoundly hearing-impaired speakers. DESIGN: Speakers were 20 Cantonese adolescents, 10 of whom had normal-hearing (mean age = 13;05); the other 10 were profoundly hearing-impaired (mean age = 13;05). The hearing-impaired speakers were selected on the basis of the criterion of being prelingually deaf; they showed pure-tone average thresholds of 90 dB HL or more in the better ear at 0.5, 1.0, and 2.0 kHz. Twenty-four consonant-vowel Cantonese words made up four sets of words that minimally contrasted in the six contrastive Cantonese tones. The words were read by the speakers once in random order. Listeners were 10 final-year speech therapy students who were asked to identify the Cantonese tones. The f0 of each syllable (tone) was measured at five consecutive positions of the vocalic segment (initial, 25%, 50%, 75%, final). Discriminant analysis was used to determine how average f0 and f0 change accounted for both the production of intended tones and the perception of correctly identified tones. RESULTS: Average f0 and f0 change over the second half of the vocalic segment were reliable acoustic and perceptual correlates of tones produced by control speakers. By contrast, for hearing-impaired speakers, production of intended tones were not reliably distinguished by average f0 or f0 change. Furthermore, listeners mainly relied on f0 change over the second half of the vocalic segment for the distinction between tone 25 and level tones (55, 33, and 22) produced by hearing-impaired speakers. CONCLUSIONS: Average f0 and f0 change over the second half of the vocalic segment are important cues for accurate identification of Cantonese tones produced by speakers with normal-hearing. By contrast, these cues are less reliable for perceiving tones produced by profoundly hearing-impaired speakers.     

The effects of changes in hearing status in cochlear implant users on the acoustic vowel space and CV coarticulation.

In order to examine the role of hearing status in controlling coarticulation, eight English vowels in /bVt/ and /dVt/ syllables, embedded in a carrier phrase, were elicited from 7 postlingually deafened adults and 2 speakers with normal hearing. The deaf adults served in repeated recording sessions both before and up to a year after they received cochlear implants and their speech processors were turned on. Each of the two hearing control speakers served in two recording sessions, separated by about 3 months. Measures were made of second formant frequency at obstruent release and at 25 ms intervals until the final obstruent. An index of coarticulation, based on the ratio of F2 at vowel onset to F2 at midvowel target, was computed. Changes in the amount of coarticulation after the change in hearing status were small and nonsystematic for the /bVt/ syllables; those for the /dVt/ syllables averaged a 3% increase--within the range of reliability measures for the 2 hearing control speakers. Locus equations (F2 at vowel onset vs. F2 at vowel midpoint) and ratios of F2 onsets in point vowels were also calculated. Like the index of coarticulation, these measures tended to confirm that hearing status had little if any effect on coarticulation in the deaf speakers, consistent with the hypothesis that hearing does not play a direct role in regulating anticipatory coarticulation in adulthood. With the restoration of some hearing, 2 implant users significantly increased the average spacing between vowels in the formant plane, whereas the remaining 5 decreased that measure. All speakers but one also reduced vowel duration significantly. Four of the speakers reduced dispersion of vowel formant values around vowel midpoint means, but the other 3 did not show this effect.     

Computational Model Predictions of Cues for Concurrent Vowel Identification

Although differences in fundamental frequencies (F0s) between vowels are beneficial for their segregation and identification, listeners can still segregate and identify simultaneous vowels that have identical F0s, suggesting that additional cues are contributing, including formant frequency differences. The current perception and computational modeling study was designed to assess the contribution of F0 and formant difference cues for concurrent vowel identification. Younger adults with normal hearing listened to concurrent vowels over a wide range of levels (25–85 dB SPL) for conditions in which F0 was the same or different between vowel pairs. Vowel identification scores were poorer at the lowest and highest levels for each F0 condition, and F0 benefit was reduced at the lowest level as compared to higher levels. To understand the neural correlates underlying level-dependent changes in vowel identification, a computational auditory-nerve model was used to estimate formant and F0 difference cues under the same listening conditions. Template contrast and average localized synchronized rate predicted level-dependent changes in the strength of phase locking to F0s and formants of concurrent vowels, respectively. At lower levels, poorer F0 benefit may be attributed to poorer phase locking to both F0s, which resulted from lower firing rates of auditory-nerve fibers. At higher levels, poorer identification scores may relate to poorer phase locking to the second formant, due to synchrony capture by lower formants. These findings suggest that concurrent vowel identification may be partly influenced by level-dependent changes in phase locking of auditory-nerve fibers to F0s and formants of both vowels.     

The Perception of Complex Harmonic Patterns by Profoundly Hearing-Impaired Listeners

In providing profoundly hearing-impaired persons with processed speech through a signal-processing hearing aid, it is important that the new speech code matches their auditory capacities. This processing capacity for auditory information was investigated in this study. In part 1, the subjects’ ability to judge similarities among 8 different but related harmonic complexes was studied. The patterns contained different numbers of harmonics to a 125-Hz fundamental frequency; the harmonics had been spread over the spectrum in various ways. The perceptual judgments appeared to be based on a temporal cue, beat strength, and a spectral cue, related to the balance of high and low frequency components. In part 2, three sets of synthetic vowels were presented to the subjects. Each vowel was realized by summing harmonically related in-phase sinusoids at two formant frequencies. The sets differed in the number of sinusoids per formant: 1, 2 or 3. It was found that the subjects used spectral cues and vowel length for differentiating among the vowels. The overall results show the limited but perhaps usable ability of the profoundly impaired ear to handle spectral information. Implications of these results for the development of signal-processing hearing aids for the profoundly hearing impaired are discussed.     

Formant frequencies of stuttered and fluent vowels

The formant frequencies of 15 adult stutterers' fluent and disfluent vowels and the formant frequencies of stutterers' and nonstutterers' fluent vowels were compared in an F1-F2 vowel space and in a normalized F1-F2 vowel space. The results indicated that differences in formant frequencies observed between the stutterers' and nonstutterers' vowels can be accounted for by differences among the vocal tract dimensions of the talkers. In addition, no differences were found between the formant frequencies of the fluent and disfluent vowels produced by the stutterers. The overall pattern of these results indicates that, contrary to recent reports (Klich & May, 1982), stutterers do not exhibit significantly greater vowel centralization than nonstutterers.     

Effect of the loss of auditory feedback on segmental parameters of vowels of postlingually deafened speakers

Objective: The most obvious and best documented changes in speech of postlingually deafened speakers are the rate, fundamental frequency, and volume (energy). These changes are due to the lack of auditory feedback. But auditory feedback affects not only the suprasegmental parameters of speech. The aim of this study was to determine the change at the segmental level of speech in terms of vowel formants. Methods: Twenty-three postlingually deafened and 18 normally hearing speakers were recorded reading a German text. The frequencies of the first and second formants and the vowel spaces of selected vowels in word-in-context condition were compared. Results: All first formant frequencies (F1) of the postlingually deafened speakers were significantly different from those of the normally hearing people. The values of F1 were higher for the vowels /e/ (418±61 Hz compared with 359±52 Hz, P=0.006) and /o/ (459±58 compared with 390±45 Hz, P=0.0003) and lower for /a/ (765±115 Hz compared with 851±146 Hz, P=0.038). The second formant frequency (F2) only showed a significant increase for the vowel/e/(2016±347 Hz compared with 2279±250 Hz, P=0.012). The postlingually deafened people were divided into two subgroups according to duration of deafness (shorter/longer than 10 years of deafness). There was no significant difference in formant changes between the two groups. Conclusion: Our report demonstrated an effect of auditory feedback also on segmental features of speech of postlingually deafened people.     

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.     

Labeling of /s/ and [see text] by listeners with normal and impaired hearing, revisited.

The two aims of this study were (a) to determine the perceptual weight given formant transition and relative amplitude information for labeling fricative place of articulation perception and (b) to determine the extent of integration of relative amplitude and formant transition cues. Seven listeners with normal hearing and 7 listeners with sensorineural hearing loss participated. The listeners were asked to label the fricatives of synthetic consonant-vowel stimuli as either /s/ or [see text]. Across the stimuli, 3 cues were varied: (a) The amplitude of the spectral peak in the 2500-Hz range of the frication relative to the adjacent vowel peak amplitude in the same frequency region, (b) the frication duration, which was either 50 or 140 ms, and (c) the second formant transition onset frequency, which was varied from 1200 to 1800 Hz. An analysis of variance model was used to determine weightings for the relative amplitude and transition cues for the different frication duration conditions. A 30-ms gap of silence was inserted between the frication and vocalic portions of the stimuli, with the intent that a temporal separation of frication and transition information might affect how the cues were integrated. The weighting given transition or relative amplitude differed between the listening groups and depended on frication duration. Use of the transition cue was most affected by insertion of the silent gap. Listeners with hearing loss had smaller interaction terms for the cues than listeners with normal hearing, suggesting less integration of cues.     

Vowel perception: experiments with a single-electrode cochlear implant

We investigated vowel perception by 15 subjects using the single-electrode cochlear implant used at the House Ear Institute in Los Angeles. Subjects were postlingually deaf adults having histories of unsuccessful hearing aid use and a minimum of 6 to 12 months experience with the implant. Eleven American English vowels spoken by a male talker were tape recorded, digitized, analyzed, and controlled for the experiments. The stimuli were audio-recordings of both natural and loudness-matched vowels. Subjects rated the dissimilarity of both the naturally spoken and the loudness-matched vowels, and performed identification of the latter. Two normal-hearing subjects served as controls for the dissimilarity tasks. Multidimensional scaling, hierarchical clustering, and percent correct identification analyses were used to help determine the perceptual features used by the subjects in their judgments. Generally, the normal-hearing subjects took advantage of second formant (F2) frequency information. The cochlear-implant users relied primarily upon fundamental (F0) and first formant (F1) frequency information and demonstrated difficulty in vowel identification. No major differences were noted for the natural versus loudness-matched vowels. F2 information, requisite for accurate vowel recognition, did not correspond to any of the perceptual dimensions discerned in the results obtained from implant subjects.     

Linear phoneme boundaries for German synthetic two-formant vowels

The phonetic boundaries of variable, synthetic two-formant vowels were studied in psychophysical tests. In the F1 versus F2 formant plane, vowel boundaries appeared to be straight and all but one were parallel to the formant axes. Discrimination of two of the eight German vowels examined relied within certain boundaries upon information of the frequency of the first formant (F1) independent of that of the second (F2) or vice versa. Two vertical F1 boundaries were common to six vowels and one horizontal F2 boundary was common to five vowels. Interpreted in the light of recent neurophysiological data these findings point to the existence of mechanisms of vowel recognition with independent assessment of the two formants.     

Preservation of second formant transitions during simultaneous communication: a locus equation perspective

This study investigated the preservation of second formant transition acoustic cues to intelligibility in speech produced during simultaneous communication (SC) from a locus equation perspective. 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 second formant frequencies in consonant-vowel-consonant (CVC) syllables. Linear regression fits made to coordinates representing second formant transition onset and offset frequencies following stop consonant release of CVC syllables (locus equations) were used to examine place of articulation cues in both SA and SC conditions. Although results indicated longer sentence durations for SC than SA, locus equation slopes and intercepts obtained from speech produced during SC were virtually identical to those obtained during SA, indicating no degradation of stop consonant acoustic cues during SC. This conclusion is consistent with previous research indicating that temporal alterations produced by SC do not involve violations of other rules of spoken English. Educational objectives: As a result of this activity, the participant will be able to (1) describe SC; (2) explain the role of SC in communication with children who are deaf; (3) describe second formant transitions in English speech; and (4) identify second formant transition patterns in speech produced during SC.     

The effect of radiofrequency volumetric tissue reduction of soft palate on voice

The surgical techniques used for snoring and OSA treatment include partial/complete resection or tissue reduction of the oropharyngeal structures such as uvula, tonsilla palatinas, soft palate, lateral pharyngeal tissues and tongue base. So it is predictable for these techniques to affect the resonating volume of the vocal tract and therefore the speech sounds. The goal of this study was to evaluate whether radiofrequency volumetric tissue reduction (RFVTR) of the soft palate can cause voice changes by altering the formant frequencies and fundamental frequency of vowels. A prospective study of 26 habitual snorers and mild obstructive sleep apnea patients (apnea–hypopnea index, <10 in all cases) were investigated before and 6 weeks after RFVTR. The patients received one Somnoplasty® RFVTR treatment of 1,400 J per treatment session: 700 J into the midline and 350 J on each side of the soft palate with a maximum temperature of 80°C. Acoustic evaluation was made by the Multidimensional Voice Program. The mean fundamental frequency (MF0) and the first three formant frequencies (F1, F2, F3) of four sustained vowels /a/, /e/, /i/ and /o/ were determined. Comparison between preoperative and postoperative acoustic analysis of the MF0 and F1, F2, F3 of sustained vowels revealed no significant change. The findings of the study indicate that RFVTR of the soft palate as a treatment for snoring and mild forms of OSA does not have a significant impact on the mean fundamental frequency and formant frequencies of vowels. These results seem to be important in management of patients with concerns about postoperative vocal quality, such as singers and professional speakers.     

The role of spectral and temporal cues in vowel identification by listeners with impaired hearing.

This study examined the use of duration and formant frequency in the labeling of synthetic CVC stimuli forming a beet-bit continuum. Durational and F2 frequency cues to vowel identity varied systematically across stimuli. Subjects with normal hearing tended to rely primarily on F2 frequency in vowel labeling, whereas subjects with impaired hearing relied less on F2 information. This group difference was observed even for stimuli with large F2 differences, which were easily discriminated by all subjects. The effect of vowel duration on labeling was similar for both groups, with long-duration stimuli receiving more "beet" responses than short-duration stimuli across the F2 range. Psychoacoustic measures of frequency resolution and temporal resolution were poor predictors of a subject's use of formant information and duration information in labeling.     

Perceptual weighting of relative amplitude and formant transition cues in aided CV syllables.

The current study explored the changes in weighting of relative amplitude and formant transition cues that may be caused by a K-amp circuit. Twelve listeners with normal hearing and 3 listeners with sensorineural hearing loss labeled the stop consonant place of articulation of synthetic consonant-vowel stimuli. Within the stimuli, two acoustic cues were varied: the frequency of the onset of the second and third formant (F2/F3) transitions and the relative amplitude between the consonant burst and the following vowel in the fourth and fifth formant (F4/ F5) frequency region. The variation in the two cues ranged from values appropriate for a voiceless labial stop consonant to a voiceless alveolar stop consonant. The listeners labeled both the unaided stimuli and the stimuli recorded through a hearing aid with a K-amp circuit. An analysis of variance (ANOVA) model was used to calculate the perceptual weight given each cue. Data from listeners with normal hearing show a change in relative weighting of cues between aided and unaided stimuli. Pilot data from the listeners with hearing loss show a more varied pattern, with more weight placed on relative amplitude. These results suggest that calculation of perceptual weights using an ANOVA model may be worthwhile in Future studies examining the relationship between acoustic information presented by a hearing aid and the subsequent perception by the listener with hearing loss.     

Consonant lingual-palatal contacts produced by normal-hearing and hearing-impaired children.

Ten normal hearing (NH) and 18 profoundly hearing-impaired (HI) children were recorded using palatometry and audiotape while producing the consonants /t,d,k,g,s,z,integral of/ in CV syllables (V = /i, a/). The lingual-palatal contacts produced by the NH subjects for the alveolar stops were undifferentiated across voicing and vowel environment differences. Lingual-palatal contact patterns for the velar stops differed for vowel environment but not for voicing. The /s/ and /z/ sibilants were distinguished by groove width but not anterior place. Groove locations for /s/ and /z/ were more anterior than groove locations for /integral of/. The anterior grove location for the /integral of/ was vowel dependent. The HI subjects produced idiosyncratic lingual-palatal contact patterns. As patterns for individuals became more unique and less variable across the syllable stimuli, listener identifications showed correspondingly incorrect, undifferentiated responses. The atypical contact patterns used by the HI subjects often required interpretation of possible tongue activities during attempts at the various consonants.     

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.     

Vowel space characteristics and vowel identification accuracy.

PURPOSE: To examine the relation between vowel production characteristics and intelligibility. METHOD: Acoustic characteristics of 10 vowels produced by 45 men and 48 women from the J. M. Hillenbrand, L. A. Getty, M. J. Clark, and K. Wheeler (1995) study were examined and compared with identification accuracy. Global (mean f0, F1, and F2; duration; and amount of formant movement) and fine-grained measures (vowel space area; mean distance among vowels; f0, F1, and F2 ranges; duration ratio between long and short vowels; and formant movement ratio between dynamic and static vowels) were used to predict identification scores. Acoustic measures of the most frequently confused pairs (/ae/-/epsilon/ and /a/-/inverted v/) were compared. RESULTS: Global and fine-grained measures accounted for less than 1/4 of variance in identification scores: Vowel space area alone accounted for 9%-12% of variance. Differences in vowel identification were largely due to poor identification of /ae/, /epsilon/, /a/, or /inverted v/. Well-identified vowels were distinctive in formant frequencies, duration, and amount of formant movement over time. CONCLUSIONS: Distinctiveness among neighboring vowels is more important in determining vowel intelligibility than vowel space area. Acoustic comparison of confused vowels may be more useful in studying intelligibility of normal and disordered speech than in measuring vowel space area.     

Perceptual weighting of stop consonant cues by normal and impaired listeners in reverberation versus noise.

PURPOSE: To determine if listeners with normal hearing and listeners with sensorineural hearing loss give different perceptual weightings to cues for stop consonant place of articulation in noise versus reverberation listening conditions. METHOD: Nine listeners with normal hearing (23-28 years of age) and 10 listeners with sensorineural hearing loss (31-79 years of age, median 66 years) participated. The listeners were asked to label the consonantal portion of synthetic CV stimuli as either /p/ or /t/. Two cues were varied: (a) the amplitude of the spectral peak in the F4/F5 frequency region of the burst was varied across a 30-dB range relative to the adjacent vowel peak amplitude in the same frequency region, (b) F2/F3 formant transition onset frequencies were either appropriate for /p/, /t/ or neutral for the labial/alveolar contrast. RESULTS: Weightings of relative amplitude and transition cues for voiceless stop consonants depended on the listening condition (quiet, noise, or reverberation), hearing loss, and age of listener. The effects of age with hearing loss reduced the perceptual integration of cues, particularly in reverberation. The effects of hearing loss reduced the effectiveness of both cues, notably relative amplitude in reverberation. CONCLUSIONS: Reverberation and noise conditions have different perceptual effects. Hearing loss and age may have different, separable effects.     

Isovowel lines for the evaluation of vowel formant structure in speech disorders

This report describes a system of isovowel lines in the F1-F2 and F2-F3 planes and demonstrates how these linear approximations to vowel formant frequencies for a diverse sample of speakers can be used to evaluate the vowel formant structures of individuals with speech disorders. The application to disordered speech is illustrated with data for dysarthric adults, deaf adolescents, and young children with developmental errors of: Formula: (See Text) production.     

Improvement in vowel articulation of deaf children.

Three deaf adolescents who had poorly developed skills in oral communication were given specialized instruction designed to improve their ability to articulate vowels. This instruction was given for 1 hour weekly over a 5-month period, and it led to an improvement in vowel articulation that was substantial enough to be measured acoustically. The instruction emphasized articulatory relations between vowel sounds that are particularly difficult for the deaf to perceive visually or vibrotactually. The formant frequencies of five vowels were measured spectrographically before and after training. The measurements showed that all three children improved in their ability to articulate vowels as indicated by an increased frequency range of the second formant, a reduced amount of overlap in the frequency plots of adjacent vowels, and in more appropriate formant frequency values for individual vowels.