Talker's Vowels Research Articles

Does Time Compression Decrease Intelligibility for Female Talkers More Than for Male Talkers?

Purpose This preliminary investigation compared effects of time compression on intelligibility for male versus female talkers. We hypothesized that time compression would have a greater effect for female talkers. Method Sentence materials from four talkers (two males) were time compressed, and original-speed and time-compressed speech materials were presented in a background of 12-talker babble to young adult listeners with normal hearing. Each talker/processing condition was heard by eight listeners (total N = 64). Generalized linear mixed-effects models were used to determine the effects of and interaction between processing condition and talker sex on keyword intelligibility. Additional post hoc analyses examined whether processing condition effects were related to talker vowel space and word frequency. Results For original-speed sentences, female and male talkers were essentially equally intelligible. Time compression reduced intelligibility for all talkers, but the effect was significantly greater for the female talkers. Supplementary analyses revealed that the effect of time compression depended on both talker vowel space and word frequency: The detrimental effect decreased significantly as word frequency and vowel space increased. Word frequency effects were also greater overall for talkers with larger vowel spaces. Conclusions While the small talker sample limits conclusions about the effects of talker sex, the secondary analyses suggest that intelligibility of talkers with larger vowel spaces is less susceptible to the negative effect of time compression, especially for high-frequency words.

Children's perception of conversational and clear American-English vowels in noise.

Much of a child's day is spent listening to speech in the presence of background noise. Although accurate vowel perception is important for listeners' accurate speech perception and comprehension, little is known about children's vowel perception in noise. Clear speech is a speech style frequently used by talkers in the presence of noise. This study investigated children's identification of vowels in nonsense words in noise and examined whether adults' use of clear speech would result in the children's more accurate vowel identification. Two female American-English (AE) speaking adults were recorded producing the nonsense word /gəbVpə/ with AE vowels /ɛ-æ-ɑ-ʌ/ in phrases in conversational and clear speech. These utterances were presented to 15 AE-speaking children (ages 5.0-8.5 years) at a signal-to-noise ratio of -6 dB. The children repeated the utterances. Clear-speech vowels were repeated significantly more accurately (87%) than conversational-speech vowels (59%), suggesting that clear speech aids children's vowel identification. Children repeated one talker's vowels more accurately than the other's, and front vowels more accurately than central and back vowels. The findings support the use of clear speech for enhancing adult-to-child communication in AE in noisy environments.

Cross-Language Perception of Cantonese Vowels Spoken by Native and Non-native Speakers

This study examined the effect of native language background on listeners' perception of native and non-native vowels spoken by native (Hong Kong Cantonese) and non-native (Mandarin and Australian English) speakers. They completed discrimination and an identification task with and without visual cues in clear and noisy conditions. Results indicated that visual cues did not facilitate perception, and performance was better in clear than in noisy conditions. More importantly, the Cantonese talker's vowels were the easiest to discriminate, and the Mandarin talker's vowels were as intelligible as the native talkers' speech. These results supported the interlanguage speech native intelligibility benefit patterns proposed by Hayes-Harb et al. (J Phonetics 36:664-679, 2008). The Mandarin and English listeners' identification patterns were similar to those of the Cantonese listeners, suggesting that they might have assimilated Cantonese vowels to their closest native vowels. In addition, listeners' perceptual patterns were consistent with the principles of Best's Perceptual Assimilation Model (Best in Speech perception and linguistic experience: issues in cross-language research. York Press, Timonium, 1995).

Cues to perceptual normalization of talker differences

To recognize vowels produced by a specific talker, a listener must know something about the talker's vowel space. How do listeners learn about a talkers' vowel space? How different must two talkers' vowels be to constitute different vowel spaces? To investigate these questions, listeners monitored sequences of target vowels for a specified target. In one condition, a single talker produced the vowels for each trial. In a second condition, a mix of four talkers produced the vowels for each trial. Previous research demonstrated that vowel recognition is accurate when talkers are mixed, but it requires more attention. The present study compared recognition for whispered and voiced vowels in these conditions to eliminate the use of F0 as a cue for talker normalization. Another experiment examined the effects of talker differences on normalization. Performance for a pair of talkers with similar vowel spaces was compared to performance for a pair of talkers with more disparate vowels. The results of these studi...

Perceptual normalization of the vowels of a man and a child in various contexts

The topic of this study is speaker normalization. Both a man and a child rapidly produced the Dutch sentences “Matroos p Vt kaas” (“Sailor p Vt eats cheese”): the man imitated the child's pitch. The test words p Vt were presented to listeners in their original carrier sentence, in isolation, and in the other talker's carrier sentence. Especially in the latter condition considerably more vowel confusions occurred. It is argued that listeners match unknown vowels with template vowels of “average” men, women or children: the appropriate template is chosen on the basis of pitch and timbre of the unknown vowels. The vowel confusions in the present experiment can thus be explained by a confusion of templates. This explanation accounts better for the test results than the one suggested by Joos (1948) and others, that the acoustic context provides information about the formant frequencies of the talker's vowels with which a vowel space can be constructed that serves as a reference frame for the identification of the vowels in the test words.

Perceptual distances between vowels located in a limited phonetic space

Knowledge of objective measures of perceptual differences between vowel spectra is of crucial importance in the design of speech coders. Toward this goal we have developed procedures for obtaining a multidimensional representation of the perceptual space over a limited vowel region. First, natural sounding vowel stimuli were synthesized using an lpc formant synthesizer. Starting with formants measured from a male talker's vowels, stimuli were generated by varying F1 and F2 in small increments. Listeners judged the dissimilarities between all pairs of vowels several times. These perceptual differences were mapped into distances between the vowels in an n-dimensional metric space using multidimensional scaling. In the first study, 11 steady-state stimuli were synthesized in the region of /i/ and /I/. Although the physical stimulus space had only two dimensions (F1 × F2), the resulting perceptual space had at least three dimensions. In this paper, perceptual spaces for stimuli located in other vowel regions, as well as for vowels embedded in a consonantal context, will be compared. Finally, we will discuss a measure of the difference between these perceptual spaces and their physical stimulus spaces calculated from nonlinear regression techniques.

Information conveyed by vowels: a negative finding

An early study with synthetic speech suggested that vowel identification includes a normalization stage, such that the listener calibrates his perceptual apparatus for each talker's vowel space [Peter Ladefoged and D. E. Broadbent, J. Acoust. Soc. Am. 29, 1 (1957)]. In the present study, no evidence for such a perceptual mechanism was obtained using natural speech. Each of a set of b-vowel-t test; words, spoken rapidly within a sentence carrier by an adult male was presented for recognition within the carrier in which It was uttered, appropriately embedded within an identical carrier produced by a second adult male with substantially different vocal tract dimensions, and excised from sentence context. The two talkers achieved the same pitch levels and speaking rate, with the result that mixed-talker sentences were perceived as if uttered by one talker. Errors in recognition were typically found only for isolated test words. Preliminary data from a replication of this design with more widely divergent vocal tracts (i.e., adult male and nine-year-old male) are similar. Apparently, some factors beyond the syllable shape the acoustic specification of vowels, though not in the sense in which normalization is traditionally defined.

Discrimination of speech sounds by the chinchilla: steady-state /i/ vs /a/

Two female and two male talkers recorded two tokens of /a/ and /i/ at each of three pitch levels. Four chinchillas were initially trained to respond differentially to single tokens of one talker's vowels. Intensity was randomly varied over 10 dB throughout. Thereafter variations of tokens, talkers, and pitch levels were singly introduced, and performance exceeding 90% correct was maintained. When the full catalog of 24/a/'s and 24/i/'s was used, performance fell to 86% correct. The decrement appeared to be related to testing variables rather than the animals' abilities. The testing procedure was modified and performance rose to 95% correct. Generalization tests showed that the animals could easily transfer to a set of 24 new talkers as well as to synthetic vowels that differed in only formant locations. The chinchilla can correctly classify novel instances of /i/ and /a/ in spite of variations from tokens, talkers, pitch levels, and intensity. [Supported by NIH Grants NS03856 to CID and RR00396 to the Biomedical Computer Laboratory of Washington University.]

Classification of self-normalized vowels

The classical vowel measurements of Peterson and Barney in 1952 have been reexamined on an individual basis to determine the minimum dimensionality required to classify a single talker's vowels, and the minimum number of vowels required to specify the dimensions. It was found that two formants are adequate for this purpose, and that no more than three vowels are required to scale the frequencies of two-formant space. Within that self-normalized space, all vowels have standard locations which are similar for all talkers.