Cortical evidence of the perceptual backward masking effect on /l/ and /r/ sounds from a following vowel in Japanese speakers

We examined the influence of stimulus duration of foreign consonant vowel stimuli on the MMNm (magnetic counter part of mismatch negativity). In Experiment 1, /ra/ and /la/ stimuli were synthesized and subjects were native Japanese speakers who are known to have difficulty discriminating the stimuli. "Short" duration stimuli were terminated in the middle of the consonant-to-vowel transition (110 ms). They were nevertheless clearly identifiable by English speakers. A clear MMNm was observed only for short-duration stimuli but not for untruncated long-duration (150-ms) stimuli. We suggest that the diminished MMNm for longer duration stimuli result from more effective masking by the longer vowel part. In Experiment 2 we examined this hypothesis by presenting only the third formant (F3) component of the original stimuli, since the acoustic difference between /la/ and /ra/ is most evident in the third formant, whereas F1 and F2 play a major role in vowel perception. If the MMNm effect depends on the acoustic property of F3, a stimulus duration effect comparable to that found with the original /la/ and /ra/ stimuli might be expected. However, if the effect is attributable to the masking effect from the vowel, no influence of stimulus duration would be expected, since neither stimulus contains F1 and F2 components. In fact, the results showed that the "F3 only" stimuli did not show a duration effect; MMNm was always elicited independent of stimulus duration. The MMN stimulus duration effect is thus suggested to come from the backward masking of foreign consonants by subsequent vowels.     

The influence of cochlear implantation on vowel articulation

PURPOSE: Speech of deaf persons differs considerably from that of speakers with normal hearing. The purpose of this study was to investigate the acoustic changes in articulation of corner vowels in deaf children and adults after cochlear implantation. METHODS: Thirteen prelingually deaf children and 12 postlingually deaf adults were included in the study. Voice samples of the isolated corner vowels /a/, /i/ and /u/ were analyzed before and 6-12 months after the implantation. The frequencies of the first (F1) and second (F2) formants, the F1/F2 ratio of all three corner vowels, and the area of the vowel triangle were calculated and compared before and 6-12 months after the implantation. RESULT: In the adults, no significant differences were detected in the formant frequencies, the F1/F2 ratio or the area of the vowel triangle. However, significant change in formant frequencies was detected in the group of 13 prelingually deaf children. After the implantation the F1 of /u/ decreased significantly, and favorable decreases of the F1 of /i/ and the F1/F2 ratio in /i/ and /u/ were close to being statistically significant. All changes caused better phonological difference between the two vowels. The significant change in the F1 of /u/ and the change of F1 of /i/ resulted in the expansion of the vowel space, which was expressed as an increase in the area of the vowel triangle. CONCLUSIONS: We suggest that in children the acquired hearing ability and further development of neuromuscular control of articulation are the reasons for the significant improvement after cochlear implantation. The results also suggest that the area of the vowel triangle is a useful and sensitive indicator of the more precise articulation after implantation. In order to achieve better and faster improvement of articulation, regular speech therapy should be included in the rehabilitation of deaf persons after cochlear implantation.     

Acoustic characteristics of vowels produced by Greek intelligible speakers with profound hearing impairment I: Examination of vowel space

Purpose: The study examines F1, F2 and F3 formant frequencies of vowels produced by six Greek intelligible speakers with profound hearing impairment and six speakers with normal hearing (three male and three female in each group).

Method: The formant frequencies are measured in words of the form /?pVCV/ where V?=?/i, ?, ?, ?, u/ and C?=?/p, t, k, s/. The study examines differences in formant frequencies between the two groups and as a function of gender. Three measures are calculated to examine the area of the vowel space and differences along the F1 and F2 axes between the groups and genders.

Result: The results show that the vowel space produced by the speakers with hearing impairment is considerably reduced. Greater reduction was evident for F2 compared to F1. Restricted formant frequency ranges and relatively large variation along F1 and/or F2 for selected vowels resulted in overlap among vowel categories. F3 frequencies were systematically lower and showed greater variation for the speakers with hearing impairment.

Conclusion: The paper discusses findings with reference to perceptual and production constraints affecting the speech of individuals with hearing impairment.     

Acoustic characteristics of vowels produced by Greek intelligible speakers with profound hearing impairment II: The influence of stress and context

Purpose: The present paper examines the influence of stress and context on selected acoustic characteristics of vowels produced by six adult Greek intelligible speakers with profound hearing impairment and six speakers with normal hearing (three males and three females in each group).

Method: F1, F2 and F3 formant frequencies and the duration of vowels are measured in words of the form /^′pVCV/ with V = /i, ?, ?, ?, u/ and C = /p, t, k, s/. Variation in these parameters due to context and stress is reported for the two genders. A co-articulatory measure and three measures that examine the area of the vowel space and differences along the F1 and F2 axes are calculated.

Result: The results show a reduction of the vowel space in the unstressed condition for both groups, while vowel duration was found to be significantly longer in this condition for the speakers with hearing impairment. In addition, smaller C-to-V carryover co-articulatory effects were found for the speakers with hearing impairment.

Conclusion: Findings are discussed within the framework of perceptual and production constraints in hearing impairment and with reference to current models of co-articulation.     

Analysis of the spectral envelope of sounds by the human brain

Spectral envelope is the shape of the power spectrum of sound. It is an important cue for the identification of sound sources such as voices or instruments, and particular classes of sounds such as vowels. In everyday life, sounds with similar spectral envelopes are perceived as similar: we recognize a voice or a vowel regardless of pitch and intensity variations, and we recognize the same vowel regardless of whether it is voiced (a spectral envelope applied to a harmonic series) or whispered (a spectral envelope applied to noise). In this functional magnetic resonance imaging (fMRI) experiment, we investigated the basis for analysis of spectral envelope by the human brain. Changing either the pitch or the spectral envelope of harmonic sounds produced similar activation within a bilateral network including Heschl's gyrus and adjacent cortical areas in the superior temporal lobe. Changing the spectral envelope of continuously alternating noise and harmonic sounds produced additional right-lateralized activation in superior temporal sulcus (STS). Our findings show that spectral shape is abstracted in superior temporal sulcus, suggesting that this region may have a generic role in the spectral analysis of sounds. These distinct levels of spectral analysis may represent early computational stages in a putative anteriorly directed stream for the categorization of sound.     

脑卒中构音障碍患者元音产出特征与言语清晰度的相关性

目的 探讨脑卒中后构音障碍患者的元音产出特征改变及其与言语清晰度之间的关系.方法 2019年10月至2020年1月,选择脑卒中后构音障碍患者19例(脑卒中组)和健康成人18例(对照组),朗读一段语音均衡材料,分析元音产出声学特征,包括下颌距、舌距、F2i/F2u、元音空间面积(VSA)、元音清晰度指数(VAI)、F1变...     

Tongue–palate contact during selected vowels in children with speech sound disorders

Abstract

There is evidence that complete tongue–palate contact across the palate during production of vowels can be observed in some children with speech disorders associated with cleft palate in the English-speaking and Japanese-speaking populations. Although it has been shown that this is not a feature of typical vowel articulation in English-speaking adults, tongue-palate contact during vowel production in typical children and English-speaking children with speech sound disorders (SSD) have not been reported in detail. Therefore, this study sought to determine whether complete tongue–palate contact occurs during production of five selected vowels in 10 children with SSD and eight typically-developing children. The results showed that none of the typical children had complete contact across the palate during any of the vowels. However, of the 119 vowels produced by the children with SSD, 24% showed complete contact across the palate during at least a portion of the vowel segment. The results from the typically-developing children suggest that complete tongue–palate contact is an atypical articulatory feature. However, the evidence suggests that this pattern occurs relatively frequently in children with SSD. Further research is needed to determine the prevalence, cause, and perceptual consequence of complete tongue–palate contact.     

English vowels produced by Cantonese–English bilingual speakers

Abstract

The present study attempted to test the postulate that sounds of a foreign language that are familiar can be produced with less accuracy than sounds that are new to second language (L2) learners. The first two formant frequencies (F1 and F2) were obtained from the 11 English monophthong vowels produced by 40 Cantonese–English (CE) bilingual and 40 native American English monolingual speakers. Based on F1 and F2, compact-diffuse (C-D) and grave-acute (G-A) values, and Euclidean Distance (ED) associated with the English vowels were evaluated and correlated with the perceived amount of accent present in the vowels. Results indicated that both male and female CE speakers exhibited different vowel spaces compared to their AE counterparts. While C-D and G-A indicated that acquisition of familiar and new vowels were not particularly different, ED values suggested better performance in CE speakers’ productions of familiar vowels over new vowels. In conclusion, analyses based on spectral measurements obtained from the English vowel sounds produced by CE speakers did not provide favourable evidence to support the Speech Learning Model (SLM) proposed by ¹⁴ Flege, J.E. (1995). Second language speech learning: Theory, findings, and problems. In W. Strange (Ed.), Speech perception and linguistic experience. Baltimore, MD: York Press. [Google Scholar]. Nevertheless, for both familiar and new sounds, English back vowels were found to be produced with greater inaccuracy than English front vowels.     

Vowel features in Turkish accented English

The present study quantified the amount of accent in English vowels produced by native adult Turkish speakers. Vowels that are present in both Turkish and English (close vowels) were compared with those that are present only in English (distant vowels). The first two formant frequencies (F1 and F2) were obtained from the 11 English monophthong vowels (/i, i, e, ε, æ, Λ, u, , o, , /) produced by 20 Turkish-accented English (TE) (10 males and 10 females) bilinguals and 20 native American English (AE) speakers. Euclidean distance (ED) was used to measure the separation between the corresponding TE and AE vowels. Perceptual experiment was also carried out to assess the amount of accent in the English produced by Turkish speakers as perceived by native monolingual English speakers. F1 and F2 values revealed that TE speakers generally were able to produce close and distant vowels comparably, with considerable amount of deviation from AE speakers. ED values for close and distant vowels were not significantly different. The amount of perceived accent indicated the precision of vowel production and was found to directly correlate with the acoustic findings.     

Vocal tract dimensional characteristics of professional male and female singers with different types of singing voices

Abstract

The present study examined the possible relationship between classification of professional singing voices and their vocal tract parameters including vocal tract length and volume, and vowel formant frequencies. Acoustic reflection technology (ART) was used to measure vocal tract length and volume of 107 professional singers: 32 tenors, 25 baritones, 27 sopranos, and 23 mezzo-sopranos. The first three formant frequencies (F1–F3) of the English vowels /a, æ, i/ produced by the professional singers were also obtained. Results indicated significantly shorter oral and vocal tract length, and smaller oral and vocal tract volume associated with sopranos when compared with mezzo-sopranos. Acoustically, sopranos had higher F1, F2, and F3 values than mezzo-sopranos. The present findings suggest that, in addition to vocal tract length, vocal tract volume may also affect formant frequencies, implying the possibility that classifying professional singing voices is based on both vocal tract length and volume information.     

Speech intelligibility, speaking rate, and vowel formant characteristics in Mandarin-speaking children with cochlear implant

The effects of the use of cochlear implant (CI) on speech intelligibility, speaking rate, and vowel formant characteristics and the relationships between speech intelligibility, speaking rate, and vowel formant characteristics for children are clinically important. The purposes of this study were to report on the comparisons for speaking rate and vowel space area, and their relationship with speech intelligibility, between 24 Mandarin-speaking children with CI and 24 age-sex-education level matched normal hearing (NH) controls. Participants were audio recorded as they read a designed Mandarin intelligibility test, repeated prolongation of each of the three point vowels /i/, /a/, and /u/ five times, and repeated each of three sentences carrying one point vowel five times. Compared to the NH group, the CI group exhibited: (1) mild-to-moderate speech intelligibility impairment; (2) significantly reduced speaking rate mainly due to significantly longer inter-word pauses and larger pause proportion; and (3) significantly less vowel reduction in the horizontal dimension in sustained vowel phonation. The limitations of speech intelligibility development in children after cochlear implantation were related to atypical patterns and to a smaller degree in vowel reduction and slower speaking rate resulting from less efficient articulatory movement transition.     

Locating the initial stages of speech-sound processing in human temporal cortex

It is commonly assumed that, in the cochlea and the brainstem, the auditory system processes speech sounds without differentiating them from any other sounds. At some stage, however, it must treat speech sounds and nonspeech sounds differently, since we perceive them as different. The purpose of this study was to delimit the first location in the auditory pathway that makes this distinction using functional MRI, by identifying regions that are differentially sensitive to the internal structure of speech sounds as opposed to closely matched control sounds. We analyzed data from nine right-handed volunteers who were scanned while listening to natural and synthetic vowels, or to nonspeech stimuli matched to the vowel sounds in terms of their long-term energy and both their spectral and temporal profiles. The vowels produced more activation than nonspeech sounds in a bilateral region of the superior temporal sulcus, lateral and inferior to regions of auditory cortex that were activated by both vowels and nonspeech stimuli. The results suggest that the perception of vowel sounds is compatible with a hierarchical model of primate auditory processing in which early cortical stages of processing respond indiscriminately to speech and nonspeech sounds, and only higher regions, beyond anatomically defined auditory cortex, show selectivity for speech sounds.     

Left thalamo-cortical network implicated in successful speech separation and identification

The separation of concurrent sounds is paramount to human communication in everyday settings. The primary auditory cortex and the planum temporale are thought to be essential for both the separation of physical sound sources into perceptual objects and the comparison of those representations with previously learned acoustic events. To examine the role of these areas in speech separation, we measured brain activity using event-related functional Magnetic Resonance Imaging (fMRI) while participants were asked to identify two phonetically different vowels presented simultaneously. The processing of brief speech sounds (200 ms in duration) activated the thalamus and superior temporal gyrus bilaterally, left anterior temporal lobe, and left inferior temporal gyrus. A comparison of fMRI signals between trials in which participants successfully identified both vowels as opposed to when only one of the two vowels was recognized revealed enhanced activity in left thalamus, Heschl's gyrus, superior temporal gyrus, and the planum temporale. Because participants successfully identified at least one of the two vowels on each trial, the difference in fMRI signal indexes the extra computational work needed to segregate and identify successfully the other concurrently presented vowel. The results support the view that auditory cortex in or near Heschl's gyrus as well as in the planum temporale are involved in sound segregation and reveal a link between left thalamo-cortical activation and the successful separation and identification of simultaneous speech sounds.     

Segmental timing of young children and adults

Young children's speech is compared to (a) adult-to-adult (A-A) normal speech, and (b) adult-to-adult (A-A) slow speech, and (c) adult-to-child (A-C) speech by measuring durations and variability of each segment in consonant-vowel-consonant CVC (CVC consonant-vowel-consonant) words. The results demonstrate that child speech is more similar to A-C speech than A-A slow speech in that it exhibits a large portion of long vowel duration in a word. However, child speech but differs from A-C speech by more noticeable lengthening of consonants. In addition, child speech exhibits an inconsistent timing relationship across segments within a word whereas durational variation in consonants and vowels was correlated in A-A speech and A-C speech. The results suggest that temporal patterns of young children are quite different from those of adults, and provide some evidence for lack of motor control capability and great variance in articulatory coordination.     

Development and testing of artificial low-frequency speech codes

In a new approach to the frequency-lowering of speech, artificial codes were developed for 24 consonants (C) and 15 vowels (V) for two values of lowpass cutoff frequency F (300 and 500 Hz). Each individual phoneme was coded by a unique, nonvarying acoustic signal confined to frequencies less than or equal to F. Stimuli were created through variations in spectral content, amplitude, and duration of tonal complexes or bandpass noise. For example, plosive and fricative sounds were constructed by specifying the duration and relative amplitude of bandpass noise with various center frequencies and bandwidths, while vowels were generated through variations in the spectral shape and duration of a ten-tone harmonic complex. The ability of normal-hearing listeners to identify coded Cs and Vs in fixed-context syllables was compared to their performance on single-token sets of natural speech utterances lowpass filtered to equivalent values of F. For a set of 24 consonants in C-/a/ context, asymptotic performance on coded sounds averaged 90 percent correct for F = 500 Hz and 65 percent for F = 300 Hz, compared to 75 percent and 40 percent for lowpass filtered speech. For a set of 15 vowels in /b/-V-/t/ context, asymptotic performance on coded sounds averaged 85 percent correct for F = 500 Hz and 65 percent for F = 300 Hz, compared to 85 percent and 50 percent for lowpass filtered speech. Identification of coded signals for F = 500 Hz was also examined in CV syllables where C was selected at random from the set of 24 Cs and V was selected at random from the set of 15 Vs. Asymptotic performance of roughly 67 percent correct and 71 percent correct was obtained for C and V identification, respectively. These scores are somewhat lower than those obtained in the fixed-context experiments. Finally, results were obtained concerning the effect of token variability on the identification of lowpass filtered speech. These results indicate a systematic decrease in percent-correct score as the number of tokens representing each phoneme in the identification tests increased from one to nine.     

Sustained responses for pitch and vowels map to similar sites in human auditory cortex

Several studies have shown enhancement of auditory evoked sustained responses for periodic over non-periodic sounds and for vowels over non-vowels. Here, we directly compared pitch and vowels using synthesized speech with a "damped" amplitude modulation. These stimuli were parametrically varied to yield four classes of matched stimuli: (1) periodic vowels (2) non-periodic vowels, (3) periodic non-vowels, and (4) non-periodic non-vowels. 12 listeners were studied with combined MEG and EEG. Sustained responses were reliably enhanced for vowels and periodicity. Dipole source analysis revealed that a vowel contrast (vowel-non-vowel) and the periodicity-pitch contrast (periodic-non-periodic) mapped to the same site in antero-lateral Heschl's gyrus. In contrast, the non-periodic, non-vowel condition mapped to a more medial and posterior site. The sustained enhancement for vowels was significantly more prominent when the vowel identity was varied, compared to a condition where only one vowel was repeated, indicating selective adaptation of the response. These results render it unlikely that there are spatially distinct fields for vowel and pitch processing in the auditory cortex. However, the common processing of vowels and pitch raises the possibility that there is an early speech-specific field in Heschl's gyrus.     

Acoustic and tongue kinematic vowel space in speakers with and without dysarthria

Purpose: The purpose is to investigate acoustic and tongue body kinematic vowel dispersion patterns and vowel space in speakers with and without dysarthria secondary to amyotrophic lateral sclerosis (ALS).

Method: Acoustic and tongue kinematic vowel spaces were examined at the same time sampling point using electromagnetic articulography in 11 speakers with dysarthria secondary to ALS and 11 speakers without dysarthria. Tongue kinematic data were collected from the tongue body sensor (～25?mm posterior from the tongue apex). A number of acoustic and tongue body kinematic variables were tested.

Result: The result showed that the acoustic and tongue kinematic vowel dispersion patterns are different between the groups. Acoustic and tongue body kinematic vowel spaces are highly correlated; however, unlike acoustic vowel space, tongue body kinematic vowel space was not significantly different between the groups.

Conclusion: Both acoustic and tongue kinematic vowel dispersion patterns are sensitive to the group difference, especially with high vowels. The tongue kinematic vowel space approach is too crude to differentiate the speakers with dysarthria secondary to ALS from speakers without dysarthria. To examine tongue range of motion in speakers with dysarthria, a more refined articulatory kinematic approach needs to be examined in the future.     

Dissociation in the neural basis underlying Chinese tone and vowel production

Neuropsychologists have debated over whether the processing of segmental and suprasegmental units involves different neural mechanisms. Focusing on the production of Chinese lexical tones (suprasegmental units) and vowels (segmental units), this study used the adaptation paradigm to investigate a possible neural dissociation for tone and vowel production. Ten native Chinese speakers were asked to name Chinese characters and pinyin (Romanized phonetic system for Chinese language) that varied in terms of tones and vowels. fMRI results showed significant differences in the right inferior frontal gyrus between tone and vowel production (more activation for tones than for vowels). Brain asymmetry analysis further showed that tone production was less left-lateralized than vowel production, although both showed left-hemisphere dominance.     

Pattern analysis of EEG responses to speech and voice: influence of feature grouping

Pattern recognition algorithms are becoming increasingly used in functional neuroimaging. These algorithms exploit information contained in temporal, spatial, or spatio-temporal patterns of independent variables (features) to detect subtle but reliable differences between brain responses to external stimuli or internal brain states. When applied to the analysis of electroencephalography (EEG) or magnetoencephalography (MEG) data, a choice needs to be made on how the input features to the algorithm are obtained from the signal amplitudes measured at the various channels. In this article, we consider six types of pattern analyses deriving from the combination of three types of feature selection in the temporal domain (predefined windows, shifting window, whole trial) with two approaches to handle the channel dimension (channel wise, multi-channel). We combined these different types of analyses with a Gaussian Naïve Bayes classifier and analyzed a multi-subject EEG data set from a study aimed at understanding the task dependence of the cortical mechanisms for encoding speaker's identity and speech content (vowels) from short speech utterances (Bonte, Valente, & Formisano, 2009). Outcomes of the analyses showed that different grouping of available features helps highlighting complementary (i.e. temporal, topographic) aspects of information content in the data. A shifting window/multi-channel approach proved especially valuable in tracing both the early build up of neural information reflecting speaker or vowel identity and the late and task-dependent maintenance of relevant information reflecting the performance of a working memory task. Because it exploits the high temporal resolution of EEG (and MEG), such a shifting window approach with sequential multi-channel classifications seems the most appropriate choice for tracing the temporal profile of neural information processing.