VCV Context Research Articles

A comparison between tongue dorsum configurations during vowel production in hypernasal speech vs typical speech

Appropriate nasalization is important for intelligible speech production and can be impacted by various disorders, including a cleft palate. Nasalization is achieved primarily through coupling the nasal and oral cavities by opening the velopharyngeal (VP) port, which introduces a variety of acoustic features. Although VP control has the primary role in nasalization, evidence suggests articulatory changes such as lip rounding (constriction) enhances acoustic features of nasality, while a downward and forward movement of the tongue dorsum in high vowels could attenuate perceptions of nasality in individuals with competent VP function. There is yet scant evidence to indicate whether such systematic changes occur in the case of VP opening. In an attempt to further understand the clinical aspect of this concept, we evaluated the tongue height and forwardness using ultrasound in three speakers with VP insufficiency (VPI) and three speakers with typical VP function to investigate the tongue configuration across two conditions. Tongue dorsum excursion and tongue positioning index were captured using Assistive Articulation Assessment (AAA) software during the production of vowels /a/ and /i/ across VCV contexts. Further results will be discussed in the meeting.

An Electropalatographic Study of Korean Fricatives /s/ and /s*/

Objectives: The present study is aimed an electropalatographic investigation of Korean fricatives /s/ and /s*/. All data from this study is based on the production of 5- adult speakers who speak Korean as their first language.Methods: Electropalatography (EPG) is an instrumental technique for showing tongue and palate contact during speech. The participants recorded /s/ and /s*/ in CV (/si/, /sɑ/, /su/, /s*i/, /s*ɑ/, /s*u/) and VCV (/ɑsi/, /ɑsɑ/, /ɑsu/, /ɑs*i/, /ɑs*ɑ/, /ɑs*u/) context using EPG and then, four variables were analyzed: row of medial groove (RMG), medial groove width (MGW), medial groove length (MGL), and maximum contact frame (MCF).Results: There was significantly greater medial groove width and maximum contact frame for / s*/ compared to /s/. The difference between /si/ and /sɑ/ was also found in the row of medial groove, medial groove width and maximum contact frame. /si/ was produced further back, and had a longer medial groove length. Also, it showed more total tongue-palate contact than /sa/.Conclusion: A various range of palatal contact patterns were found between typical adults for perceptually normal /s/ and /s*/. The results provided the information about tongue–palate pattern of Korean fricatives /s/ and /s*/. These findings would be utilized to build the basic data and useful information for Korean EPG system.

Acoustic analysis of Korean stop sounds in patients with dysarthrias

Purpose Korean ‘stops’ are considered an especially good acoustic variable since they are sensitive to speech intelligibility and reflect physiological coordination between laryngeal and supra-laryngeal mechanisms. The purpose of the study was to evaluate the acoustic characteristics of both the dysarthria and control groups in the production of nine Korean stops, /p, p′, ph, t, t′, th, k, k′, kh/, in VCV contexts. Methods The participants comprised eight patients with dysarthria and eight age- and gender-matched normal adults. After the acoustic analysis of the closure duration, aspiration duration, and the ratio of closure duration to closure-aspiration combined duration, the results were compared among three types of phonation and places of articulation for Korean stops. Results The dysarthria group (DG) had longer closure durations, suggesting slower articulatory movements of the DG than the normal control group (NC). Although statistically not significant except for /ap′a/ and /at′a/, the absolute aspiration durations of the DG were still longer than those of the NC. This resulted in the normal levels of ratios in the DG between closure duration and closure-aspiration combined durations. Furthermore, the DG could change the durational aspects of stop production distinctively according to types of phonation more than they could according to the places of articulation. This trend was more prominent during the closure duration than during the aspiration duration. Conclusions This finding suggested that while the DG has centralized tongue positions, they control the tenseness and the timing coordination between laryngeal and supra-laryngeal articulators to distinctively produce different types of phonation of stops. Keywords: Dysarthria; Acoustic analysis; Korean stops; Closure duration; Aspiration duration

Design of Optimized Wavelet Packet Algorithm to Improve Perception of Sensorineural Hearing Impaired

A novel optimized wavelet packet algorithm is proposed to improve the perception of sensorineural hearing-impaired people. In this work, we have developed optimized wavelet packet along with, biorthogonal wavelet basis functions using MATLAB Code. Here, we have created eight bands based on auditory filters of quasi octave bandwidth. Evaluation was carried out by conducting listening tests on seven subjects with bilateral mild to severe sensorineural hearing loss. The speech material used for the listening test consisted of a set of fifteen nonsense syllables in VCV context. The test results show that the proposed algorithm improves the recognition score, speech quality and transmission of overall feature specifically over the unprocessed signal. The response time also reduces significantly.

Spectral discrimination of consonants for English and Chinese Listeners

Previous work in our laboratory showed that Chinese listeners had significantly higher thresholds for vowel formant discrimination than American English listeners, possibly due to a sparse vowel system in Chinese but a crowded vowel space in American English. Considering that the two languages have similar consonant densities (i.e., similar numbers of consonants), we hypothesized that English and Chinese listeners might have similar thresholds of spectral discrimination of consonant stimuli. Thresholds of spectral shift in the English consonant, /s/, were measured in an isolated form and in a VCV context for both English and Chinese listeners. Preliminary results showed that there was no significant difference in consonant discrimination thresholds between the two groups of listeners for either isolated or VCV consonants. These findings support that phonemic density may play an important role in spectral discrimination of speech sounds.

MRI study of coarticulation in European Portuguese

For this study, a small part of a recently acquired MRI database for European Portuguese (EP) was used. The sounds studied were the 12 EP voiced and unvoiced fricatives and stop consonants, produced in a symmetric VCV context. The vowels chosen were the cardinal vowels [i, a, u]. The speaker sustained the fricative sounds and maintained stop articulation during the 5.6 s of the acquisition time (T1 TSE sequence). The contours were obtained using the seeded region growing method. The influence of the seed placement was evaluated through the generation of 100 contours, with random seeds, for each sound. It was possible to verify, for the EP, some facts already reported by other authors relative to coarticulation in other languages. In general, EP stops are less resistant to coarticulatory effects than fricatives. The EP sounds presenting the highest resistance to coarticulation are the unvoiced postalveolar fricative [∫] and corresponding voiced fricative. As an example of other relevant results, for stops [t], [d] and fricative [s] there is no significant effect of the vowel in the region tongue blade region, being the influence evident in the production of the stops [k] and [g]. [Work supported by FCT, Portuguese Research Agency, by Project HERON POSC/PLP/57680/2004.]

Acoustic patterns of Japanese voiced velar stops

This presentation focuses on Japanese voiced velar /g/. The phoneme /g/ in VCV contexts is said to be characterized by a distinctive wedge-shaped formant pattern in which F2 and F3 converge toward one frequency in the transition from vowel to stop closure, and then diverge as the vocal tract opens from the stop release to the following vowel. This pattern was examined using acoustic and kinematic data from an x-ray microbeam database of Japanese speakers, which is comparable to the English language x-ray microbeam speech production database [Hashi et al., J. Acoust. Soc. Am. 104, 2426–2437 (1998)]. Japanese speakers produced the expected wedge-shaped formant pattern in isolated VCV nonsense syllables, but rarely, if ever, produced this pattern in connected speech. In contrast, English speakers more frequently produced the expected formant pattern in connected speech, though the pattern was less reliably present than in isolated VCVs and varied considerably within and across speakers. These observations highlight substantial differences between controlled laboratory speech and meaningful connected speech, as well as differences in the ways that phonemes are manifested by different linguistic communities. These data also potentially illuminate the relationship among phonetic, acoustic, and kinematic levels of speech production.

Acoustic characteristics of clearly produced fricatives

Research suggests that speakers can adopt a speaking style that allows them to be understood more easily when confronted with difficult communication situations, but few studies have examined the acoustic properties of clearly produced consonants in detail. This study attempts to characterize the type and magnitude of adaptations in the clear production of English fricatives in a carefully controlled range of communication situations. Ten female and ten male talkers produced nonsense syllables containing the eight English fricatives in VCV contexts, both in a conversational style and in a clear style (elicited by means of feedback consisting of simulated recognition errors received from an interactive computer program). Acoustic measurements were taken for spectral, amplitudinal, and temporal properties known to influence fricative recognition. Results illustrate that (1) there were some consistent overall clear speech effects, several of which (consonant duration, spectral peak location, spectral moments) were consistent with previous findings and a few (notably consonant-to-vowel intensity ratio) which were not; (2) ‘‘contrastive’’ differences related to eliciting prompts were observed in a few key comparisons; and (3) talkers differed widely in the types and magnitude of acoustic modifications.

Vocal fundamental frequency drop during VCV productions in Japanese speakers

Vocal fundamental frequency (fo) drop in relation to changes in intraoral pressure (Po) was investigated for adult male and female speakers of Japanese producing /b/ and /v/ in VCV contexts. Three experiments were conducted to examine the following effects on fo drop: (1) vocal tract constriction, (2) vowel context, and (3) speech rate. The results showed that the fo drop from vowels to a consonant was greater for /aba/ than for /ava/; it was greater for high vowel contexts, /ibi/, /abi/, /iba/, than for a low vowel context, /aba/. Speech rate changes with metronome and self-paced had variable effects on the fo drop. Overall, the fo drop for /aba/ ranged from 4% to 13% or from 0.75 to 2.17 semitones. Comparisions with English speakers will be reported. Effects of gender, vocal pitch, and intensity levels, and accent may be discussed.

The effect of masking and filtering of envelope modulations on the recognition of consonants

Consonant identification scores were obtained for 18 Dutch consonant phonemes in VCV context, in two experiments in which the narrow-band envelopes of the speech stimuli were manipulated by masking or filtering. For this purpose, the speech stimuli were split up into 26 frequency bands, each one critical band wide. The amplitude envelope of each band, as obtained with a Hilbert transform, was disturbed in two ways: (1) by a narrow-band envelope masker around 4, 8, and 12 Hz, and (2) by notch-band filtering around the same frequencies. Next the speech stimuli were synthesized by using narrow-band noise carriers, each a critical band wide, which were modulated by the aforementioned envelopes. Ten normal-hearing subjects participated in the experiments. The confusion matrices were analyzed by means of multidimensional scaling techniques and compared between the two manipulation methods. The results of the filtering experiment show that consonant recognition scores behave like a low-pass function of notch-width when expressed in octaves. The differences with the results of modulation masking will be discussed, especially with respect to modulation transfer function and consonant recognition cues.

A nonlinear dynamical systems analysis of fricative consonants

Acoustic waveforms of the strident fricatives /s/, /z/, /integral of/, and /3/ spoken by two native American English speakers are analyzed using modern chaotic analysis techniques. Fricative data are extracted from both intervocalic and sustained utterances. For comparison, acoustic waveforms of the vowels /a/, /i/, and /u/ are also analyzed. For 44% of the unvoiced fricative tokens in VCV contexts and 59% of the sustained voiced fricatives, indications of low-dimensional dynamics could be found with the given limitations of stationarity. The low-dimensional chaotic behavior is exhibited by a correlation dimension (D2) ranging between 3 and 7.2, and by positive maximum Lyapunov exponents (LEs). For the remaining fricatives, results suggest that the dimensional complexity therein is greater than the maximum D2 value that could be reliably estimated from the available data (about 7.8 for the intervocalic cases and 9 for the sustained cases). Intervocalic voiced fricatives are excluded from the analysis due to stationarity requirements. Analysis of vowels, on the other hand, indicates nonchaotic behavior demonstrated by folded limit cycles and nonpositive maximum LEs; this is consistent with results of previous studies. Findings are interpreted in terms of posited articulatory and aerodynamic parameters of turbulence in the production of fricative consonants.

The role of voice pitch in the perception of glottal stops

Glottal stops that occur in VCV context are often not realized as stops at all, but rather show voicing that is continuous throughout the ‘‘occlusion’’ interval. Glottal stops that are realized in this way are apparently marked by reductions in intensity and fundamental frequency. In the present study recordings were made of speakers producing glottal stops in utterances such as ‘‘oh–oh’’ in which a glottal stop separates two identical vowels. The utterances were resynthesized in three ways: (1) with a flat F0 contour and an intensity contour matching the original utterance, (2) with a flat intensity contour and an F0 contour matching the original utterance, and (3) with intensity and F0 contours matching the original utterance. Results suggest that either cue alone is sufficient to signal the presence of the glottal stop. The impression of most listeners was that the signals cued by intensity alone were quite similar to those cued by F0 alone. The apparent equivalence of loudness and pitch in signaling the presence of a glottal stop would seem to present difficulties for a straightforward auditory account of phonetic recognition.

Density of voicing information in purely temporal consonant identification

Speech waveforms containing purely temporal information (i.e., flat spectra and instantaneous amplitudes identical to natural speech, obtained by randomly changing the polarity of consecutive samples) contain quasiperiodic fluctuations in amplitude coincidental with voice periods. The temporal complexity of such waveforms can be reduced by half-wave rectifying the speech prior to removal of the spectral information. This study addresses the question of whether such simplification of the waveform improves the transfer of voicing information in a VCV context in normal hearing adults. The results of consonant identification experiments will be presented in which (a) the two polarities of half-wave rectification are compared to the unrectified condition (equivalent to full-wave rectification) and (b) the waveforms are low-pass filtered at the upper extreme of the fundamental frequency distribution of the speaker, prior to full-wave or half-wave rectification and removal of spectral information. Such filtering removes much of the quasi-periodicity arising from voicing in the full-wave rectified condition. [Work supported by the MRC UK.]

Articulatory and acoustic study of consonant production in a traumatically brain injured speaker.

This study examined the clinical utility of instrumental studies of the speech of neurologically impaired persons, as well as documented the particular articulatory patterns of one individual, a right-handed 36-yr-old female, 5-yr post onset of TBI, with right hemiparesis. Communicative impairments included relatively mild cognitive deficits and moderate-to-severe hypokinetic dysarthria. The speech sample included repetitions of isolated sustained continuant consonants, of VCV disyllables, and of sentences containing consonant clusters. The articulatory data were electropalatographic (EPG) signals recorded using a RION soft artificial palate with a sampling rate of 64 fps. The acoustic signals were recorded simultaneously with the EPG signals and subjected to spectral analysis. Vowel environment was found to have a strong influence on lingual contact patterns for /s/. In general, within vowel height groups, the extent of lingual contact for /s/ was greater in the VCV context than in words produced in sentences. Spectral patterns associated with differences in lingual contact for /s/ will be described. [Work supported by NIH Grant No. DC-00121 to Haskins Lab.]

Perception of Persian uvular and velar stop consonants by speakers of American English

Recent cross‐language studies by Werker and Tees [J. Acoust. Soc. Am. 75, 1866–1878 (1984)] describe difficulties in English speakers' perception of a Thompson glottalized uvular‐velar stop contrast. However, the acoustic information that differentiated the contrasting phones was difficult to specify. The present study extends the examination of non‐English place contrasts by investigating native English speakers' ability to perceive a nonglottalized uvular‐velar contrast in Persian (Farsi). Multiple instances of velar and uvular stop consonants produced in several VCV contexts by a native speaker of Farsi were presented. Correct identification of the medial consonant varied systematically as a function of vowel context from very few errors to near change performance. Acoustic analysis revealed systematic F2 and F3 formant transition differences between uvular and velar consonants produced in the same vowel context. Variations in voicing offset (murmur) were also observed in several vowel contexts. These results further our understanding of the role of linguistic experience in the perception of phonetic categories. [Research supported by NINCDS.]

Patterns of interarticulator phasing relations

The difficulty in identifying phonetic segments in the acoustic signal of speech is a commonly recognized problem. One proposed solution is that the integrity of individual segments is maintained by stable timing relations between the articulators. Recently, Kelso and Tuller [e.g., J. Acoust. Soc. Am. Suppl. 1 77, S53 (1985)] reported an invariant relation between jaw and lip gestures in various VCV contexts. Specifically, the onset of upper lip lowering for the intervocalic consonant was found to have a constant relation to the vowel‐to‐vowel jaw cycle in both time and position‐velocity phase‐plane domains. In this paper, we examine the additional effects of syllable affiliation and intervening consonant identity. The data show that the upper lip's lowering onset, relative to the position‐velocity state of the jaw (phase angle), varied as a function of speaking rate and stress. In addition, the position of the syllable boundary (before or after the intervocalic consonant) and the consonant identity (p vs...

An analysis of consonant confusions by single‐channel cochlear implant users

Four cochlear implant subjects fitted with single‐channel sound processors identified consonants taken from a 23‐consonant set and spoken in a VCV context. The videotaped VCV items were presented in three conditions: lipreading alone, stimulation alone, and stimulation plus lipreading. The subjects had had no training or testing with VCVs prior to the tests reported here. Tests were conducted within the first 0–8 months of the first fitting of the wearable single‐channel processor. A total of 7590 identifications were collected and analyzed. All subjects scored near 30% correct in the lipreading alone condition, but 3%–12% correct (near chance) in the stimulation alone condition. A broader range of scores obtained when stimulation was added to lipreading (30%–55% correct). Errors were classified in terms of three features: voicing, and place and manner of articulation. Detailed scrutiny of the error profiles indicates that beyond improving the overall percent correct identification, the addition of stimulation to lipreading allows subjects to make fewer two‐ and three‐feature confusions, narrowing down the choice of alternatives to those that differ by a single feature. [Work supported by NIH.]

Aerodynamic and palatographic characteristics of the early stages of speech adaptation to a dental appliance

Subjects were recorded speaking with a dental appliance, similar to an orthodontic retainer, which had 4 mm of thickness in the alveolar region. Comparisons were made between initial attempts to speak with such an appliance and speech after two weeks of adaptation. Data consisted of oral air flow, peak intraoral pressure, dynamic electropalatography and the microphone signal. Focus was on /s/ in VCV contexts. The very first utterance showed deviations in timing of airflow characteristics in relation to devoicing, which were rapidly corrected. Aerodynamic and palatographic evidence of smaller articulatory constriction for /s/ was also seen initially, but this feature was not adjusted adequately in the early speech attempts.

Some aerodynamic characteristics of plosive consonants produced by hearing-impaired speakers.

The purpose of this study was to investigate the rate of oral air flow for plosive consonants produced by 10 normal hearing adult males, 10 hearing-impaired adult males who demonstrated intelligible speech, and 10 hearing-impaired adult males with semi-intelligible speech. The peak rate of oral air flow was measured during production of CV and VCV syllables consisting of the vowels /a/ and /i/ and the consonants /b/, /p/, /d/, and /t/. In general, the results indicated that a significant voiced/voiceless distinction, for rate of air flow, occurred for the normally hearing and intelligible hearing-impaired subjects but not for the semi-intelligible subjects. In addition, the semi-intelligible hearing impaired, in the CV context, produced voiced plosives with significantly greater air flow and voiceless plosives with significantly less air flow; and, produced both voiced and voiceless plosives, in the VCV context, with significantly less air flow, when compared with the normally hearing and intelligible hearing-impaired speakers.

Accessing phonetic information during perceptual integration of temporally distributed cues

A group of untrained subjects, as well as several experienced listeners, participated in two forced-choice reaction time experiments requiring discrimination between two different stop consonants in VCV context. The duration of the silent closure interval in the test utterances was varied to derive functions relating response latencies to closure duration. These functions indicated that untrained subjects responded in part, and experienced listeners responded exclusively, to the VC formant transitions, which preceded the closure. Given that, at closure durations below 200 ms, the phonetic information conveyed by pre- and post-closure cues (VC and CV formant transitions) is integrated into a single phonemic percept — that of an intervocalic stop consonant at a certain place of articulation — the present results indicate that phonetic information can be accessed during perceptual integration of temporally distributed cues, and by implication, that phonetic information is continuously extracted from the speech signal.