Ratree Wayland

Acoustic characteristics of English fricatives

This study constitutes a large-scale comparative analysis of acoustic cues for classification of place of articulation in fricatives. To date, no single metric has been found to classify fricative place of articulation with a high degree of accuracy. This study presents spectral, amplitudinal, and temporal measurements that involve both static properties (spectral peak location, spectral moments, noise duration, normalized amplitude, and F2 onset frequency) and dynamic properties (relative amplitude and locus equations). While all cues (except locus equations) consistently serve to distinguish sibilant from nonsibilant fricatives, the present results indicate that spectral peak location, spectral moments, and both normalized and relative amplitude serve to distinguish all four places of fricative articulation. These findings suggest that these static and dynamic acoustic properties can provide robust and unique information about all four places of articulation, despite variation in speaker, vowel context, and voicing.

Acoustic correlates of breathy and clear vowels: the case of Khmer

Abstract This study investigates acoustic correlates of the putative breathy and clear phonation type contrast in a dialect of Khmer (Cambodian) spoken in Chanthaburi Province, Thailand. The goal is to determine whether this Khmer dialect still preserves this historical contrast. Out of seven acoustic parameters measured, four, namely * H 1 − * H 2 , * H 1 −A 1 , * H 1 − * A 3 , and vowel RMS amplitude successfully distinguished between breathy and clear vowels, with * H 1 − * H 2 measured at the beginning of the vowel being the most robust cue. However, the use of these cues varied from speaker to speaker. The * H 1 − * H 2 measurement obtained from male speakers’ production suggested that the contrast being realized may be that of a tense versus lax voice rather than a breathy versus clear voice. It is concluded that the historical breathy and clear phonation distinction in Khmer is preserved among female speakers, but this distinction may be disappearing or have become a tense versus lax distinction among male speakers.

Effects of native language and training on lexical tone perception: An event-related potential study

Tone languages such as Thai use pitch differences to distinguish lexical meaning. Previous behavioral studies have reported that naïve listeners can discriminate among lexical tones, but that native language background affects performance. The present study uses ERPs to determine whether native speakers of a tone language (Mandarin Chinese) and of a non-tone language (English) differ in their pre-attentive discrimination among Thai lexical tones, and whether training has a different effect in these two language groups. EEGs were obtained from 10 native Mandarin Chinese speakers, 10 English and 10 Thai speakers in an oddball paradigm: The Thai syllable [k(h)a:] pronounced with a high rising or low falling tone, was presented as an infrequent deviant amidst a standard mid level tone [k(h)a:] syllable, while participants watched a silent movie. Next, the Chinese and English participants completed a 2-day perceptual identification training on the mid level and low falling tones, and returned for a post training EEG. The low falling tone deviant elicited a Mismatch Negativity (MMN) in all participant groups before and after training; the high rising deviant elicited no, or a smaller, MMN, which became larger after training only in the English group. The high rising deviant also elicited a later negativity (350-650 ms) versus the mid level standard, which decreased after training in the Chinese group. These results suggest that non-Thai speakers can pre-attentively discriminate among Thai tones, but are sensitive to different physical properties of the tones, depending on their native language. English speakers are more sensitive to early pitch differences, whereas native speakers of Mandarin Chinese are more sensitive to the (later) pitch contour.

Perceptual discrimination of Thai tones by naive and experienced learners of Thai

This study investigated the ability to discriminate the middle and low tone contrasts in Thai by two groups of native English (NE) speakers and a control group of native Thai (NT) speakers. The first group was comprised of NE speakers who had no prior experience with Thai, whereas subjects in the second group were experienced learners of Thai (EE). The variables under investigation were experience with Thai, discrimination of open versus closed syllables, and the interstimulus interval (ISI) of the presentation (500 vs 1500 ms). The results obtained indicated that the NT group obtained higher discrimination scores than the NE or EE groups, the EE group obtained higher discrimination scores than the NE group, all three groups of subjects found open syllables to be more difficult to discriminate than closed syllables, and subjects in the EE group obtained higher discrimination scores for open syllables in the shorter than the longer ISI condition.

Thai lexical tone perception in native speakers of Thai, English and Mandarin Chinese: An event-related potentials training study

BackgroundTone languages such as Thai and Mandarin Chinese use differences in fundamental frequency (F0, pitch) to distinguish lexical meaning. Previous behavioral studies have shown that native speakers of a non-tone language have difficulty discriminating among tone contrasts and are sensitive to different F0 dimensions than speakers of a tone language. The aim of the present ERP study was to investigate the effect of language background and training on the non-attentive processing of lexical tones. EEG was recorded from 12 adult native speakers of Mandarin Chinese, 12 native speakers of American English, and 11 Thai speakers while they were watching a movie and were presented with multiple tokens of low-falling, mid-level and high-rising Thai lexical tones. High-rising or low-falling tokens were presented as deviants among mid-level standard tokens, and vice versa. EEG data and data from a behavioral discrimination task were collected before and after a two-day perceptual categorization training task.ResultsBehavioral discrimination improved after training in both the Chinese and the English groups. Low-falling tone deviants versus standards elicited a mismatch negativity (MMN) in all language groups. Before, but not after training, the English speakers showed a larger MMN compared to the Chinese, even though English speakers performed worst in the behavioral tasks. The MMN was followed by a late negativity, which became smaller with improved discrimination. The High-rising deviants versus standards elicited a late negativity, which was left-lateralized only in the English and Chinese groups.ConclusionResults showed that native speakers of English, Chinese and Thai recruited largely similar mechanisms when non-attentively processing Thai lexical tones. However, native Thai speakers differed from the Chinese and English speakers with respect to the processing of late F0 contour differences (high-rising versus mid-level tones). In addition, native speakers of a non-tone language (English) were initially more sensitive to F0 onset differences (low-falling versus mid-level contrast), which was suppressed as a result of training. This result converges with results from previous behavioral studies and supports the view that attentive as well as non-attentive processing of F0 contrasts is affected by language background, but is malleable even in adult learners.

Effects of musical experience and training on pitch contour perception

Abstract This study examined the effects of musical experience and training on pitch contour perception among speakers of a non-tonal language. Fifteen musicians and fifteen non-musicians from various non-tonal language backgrounds were administered pitch contour categorial discrimination baseline task before and after a two-day pitch contour identification training. Although musicians were relatively more accurate than non-musicians in pitch contour identification, their pitch contour abstraction and categorization ability was comparable to that of non-musicians. Pitch contour identification training improved both pitch contour identification and pitch contour abstraction and categorization abilities to the same degree in musicians and non-musicians. In addition, the advantage of the rising pitch contour over the falling pitch contour was observed in both tasks and among both groups of participants. Together, these results suggest that musical experience sharpened the perception of pitch among musicians, but that the auditory systems of both groups are experience-dependent and comparably malleable.

Acoustic and perceptual investigation of breathy voice

Although breathy voice is typically characterized by an increase in spectral noise, it is notoriously difficult to devise a computational method to distinguish breathy from clear (modal) voice. The present study successfully makes use of an algorithm, originally developed to quantify aspects of pathological voice quality [G. de Krom, J. Speech Hear. Res. 36, 254–266 (1993)], which computes a harmonics‐to‐noise ratio (HNR). The algorithm calculates the harmonics‐to‐noise ratio using a comb filter defined in the cepstrum domain to separate the harmonics from the noise. Performance of the algorithm was tested on three speakers (2 male, 1 female) of Javanese producing a word list of 31 minimal breathy/clear word pairs. Results showed that the algorithm reliably distinguished breathy from clear tokens for all three speakers, with higher HNRs for clear than for breathy tokens. Moreover, accurate performance was obtained for nearly all frequency ranges investigated (60–2000 Hz, 2000–3000 Hz, 3000–5000 Hz). A com...

Perception of cross‐language vowel differences: A longitudinal study of native Spanish learners of English

The study evaluated the ability of native Spanish speakers to perceive phonetic differences between Spanish vowels (/i e a o u/) and English vowels (/ieIɑoʊu/). Eighteen adult native speakers of Spanish who were learning English as a second language (L2) in Birmingham. AL were tested at 6‐month intervals over a 3.5‐year period (T1–T7). Five tokens of each Spanish and English vowel were randomly presented for classification in terms of one of the five vowels of Spanish, and were rated for goodness of fit on a 6‐point scale (where 0 indicated ‘‘not Spanish’’ and 5 indicated a ‘‘good example’’ of a Spanish vowel). At both T1 and T7, English /i/, /eI/, /ɑ/, /oʊ/ and /u/ were usually classified as Spanish /i/, /e/, /a/, /o/ and /u/, respectively. A group analysis revealed that significantly higher ratings were given to the Spanish than English member of the /o/‐/oʊ/, /u/‐/u/, /e/‐/eI/ and /a/‐/ɑ/ pairs but not the /i/‐/i/ pair. However, the number of individual L2 learners who gave significantly higher ratings to a Spanish vowel than to the corresponding English vowel differed substantially (/o/‐/oʊ/ n=18, /u/‐/u/ n=8, /e/‐/eI/ n=5, /a/−/ɑ/ n=1, /i/‐/i/n=1). Possible explanations for these between‐pair differences —acoustic and perceptual—will be discussed. [Work supported by NIH.]

Perceptual assimilation and categorical discrimination of Korean stop consonants by native Thai speakers

This study examined cross language perceptual assimilation and cross language categorical discrimination. Experiment 1 assessed the native Thai speakers’ ability to discriminate pairs of Korean stop consonants (plain, aspirated, reinforced) at three places of articulation (bilabial, alveolar, and velar). Experiment 2 assessed the perceived relation between the three classes of Korean stop consonants and the three classes of Thai stop consonants (voiced, voiceless unaspirated, voiceless aspirated). Preliminary results suggested that, in general, native Thai speakers assimilated the Korean plain and aspirated stops to the Thai aspirated stops, and the Korean reinforced stops to the Thai unaspirated stops. Results of the categorical discrimination revealed that native Thai speakers were able to successfully discriminate pairs of Korean stop consonants and that there was no relationship between their perceptual assimilation patterns and their ability to discriminate Korean stop consonants. Since the main perc...

Acoustic properties of English fricatives

A fundamental issue in speech research concerns whether distinctions in terms of place of articulation are more succesfully captured by local (static) or global (and/or dynamic) properties of the speech signal. While most studies of place of articulation have investigated stop consonants, it is uncertain whether these properties can successfully classify fricatives. In the present study, both static and dynamic metrics were used to investigate place of articulation in fricatives. Static metrics include spectral peak location, noise duration, and noise amplitude; dynamic metrics include relative amplitude, locus equations, and spectral moments. Twenty speakers produced the fricatives /f, v, θ, ð, s, z, ∫, ȝ/ followed by the vowels /i, e, ae, ɑ, o, u/. Preliminary results based on ANOVA and discriminant analysis suggest that all metrics could distinguish nonsibilant /f, v, θ, ð/ from sibilant /s, z, ∫, ȝ/. In addition, spectral moments separated /s, z/ from /∫, ȝ/ with about 95% accuracy and /f, v/ from /θ, ð/ with about 65% accuracy while locus equations only served to separate labiodental /f, v/ from all other fricatives. Accuracy of the metrics will also be compared to human perception data. [Work supported by NIH.]