Coding pitch differences in voiceless fricatives: Whispered relative to normal speech

Contrastive Alveolar/Retroflex Phonemes in Singapore Mandarin Bilinguals: Comprehension Rates for Articulations in Different Accents, and Acoustic Analysis of Productions

The standard Beijing variety of Mandarin has a clear alveolar-retroflex contrast for phonemes featuring voiceless sibilant frication (i.e., /s/, /ʂ/, /ʈs/, /ʈʂ/, /ʈsʰ/, /ʈʂʰ/). However, some studies show that varieties in the 'outer circle', such in Taiwan, have a reduced contrast for these speech sounds via a process known as 'deretroflexion'. The variety of Mandarin spoken in Singapore is also considered as 'outer circle', as it exhibits influences from Min Nan varieties. We investigated how bilinguals of Singapore Mandarin and English perceive and produce speech tokens in minimal pairs differing only in the alveolar/retroflex place of articulation. In all, 50 participants took part in two tasks. In Task 1, participants performed a lexical identification task for minimal pairs differing only the alveolar/retroflex place of articulation, as spoken by native speakers of two varieties: Beijing Mandarin and Singapore Mandarin. No difference in comprehension of the words was observed between the two varieties indicating that both varieties contain sufficient acoustic information for discrimination. In Task 2, participants read aloud from the list of minimal pairs while their voices were recorded. Acoustic analysis revealed that the phonemes do indeed differ acoustically in terms of center of gravity of the frication and in an alternative measure: long-term averaged spectra. The magnitude of this difference appears to be smaller than previously reported differences for the Beijing variety. These findings show that although some deretroflexion is evident in the speech of bilinguals of the Singaporean variety of Mandarin, it does not translate to ambiguity in the speech signal.

Communicative constraints affect oro-facial gestures and acoustics: Whispered vs normal speech

The present paper investigates a relationship between the acoustic signal and oro-facial expressions (gestures) when speakers (i) speak normally or whisper, (ii) do or do not see each other, and (iii) produce questions as opposed to statements. To this end, we conducted a motion capture experiment with 17 native speakers of German. The results provide partial support to the hypothesis that the most intensified oro-facial expressions occur when speakers whisper, do not see each other, and produce questions. The results are interpreted in terms of two hypotheses, i.e., the "hand-in-hand" and "trade-off" hypotheses. The relationship between acoustic properties and gestures does not provide straightforward support for one or the other hypothesis. Depending on the condition, speakers used more pronounced gestures and longer duration compensating for the lack of the fundamental frequency (supporting the trade-off hypothesis), but since the gestures were also enhanced when the listener was invisible, we conclude that they are not produced solely for the needs of the listener (supporting the hand-in-hand hypothesis), but rather they seem to help the speaker to achieve an overarching communicative goal.

Identification of Minimal Pairs of Japanese Pitch Accent in Noise-Vocoded Speech

The perception of lexical pitch accent in Japanese was assessed using noise-excited vocoder speech, which contained no fundamental frequency (fo) or its harmonics. While prosodic information such as in lexical stress in English and lexical tone in Mandarin Chinese is known to be encoded in multiple acoustic dimensions, such multidimensionality is less understood for lexical pitch accent in Japanese. In the present study, listeners were tested under four different conditions to investigate the contribution of non-fo properties to the perception of Japanese pitch accent: noise-vocoded speech stimuli consisting of 10 3-ERBN-wide bands and 15 2-ERBN-wide bands created from a male and female speaker. Results found listeners were able to identify minimal pairs of final-accented and unaccented words at a rate better than chance in all conditions, indicating the presence of secondary cues to Japanese pitch accent. Subsequent analyses were conducted to investigate if the listeners' ability to distinguish minimal pairs was correlated with duration, intensity or formant information. The results found no strong or consistent correlation, suggesting the possibility that listeners used different cues depending on the information available in the stimuli. Furthermore, the comparison of the current results with equivalent studies in English and Mandarin Chinese suggest that, although lexical prosodic information exists in multiple acoustic dimensions in Japanese, the primary cue is more salient than in other languages.

Adjustment of cue weighting in speech by speakers and listeners: Evidence from amplitude and duration modifications of Mandarin Chinese tone

Speech contrasts are signaled by multiple acoustic dimensions, but these dimensions are not equally diagnostic. Moreover, the relative diagnosticity, or weight, of acoustic dimensions in speech can shift in different communicative contexts for both speech perception and speech production. However, the literature remains unclear on whether, and if so how, talkers adjust speech to emphasize different acoustic dimensions in the context of changing communicative demands. Here, we examine the interplay of flexible cue weights in speech production and perception across amplitude and duration, secondary non-spectral acoustic dimensions for phonated Mandarin Chinese lexical tone, across natural speech and whispering, which eliminates fundamental frequency contour, the primary acoustic dimension. Phonated and whispered Mandarin productions from native talkers revealed enhancement of both duration and amplitude cues in whispered, compared to phonated speech. When nonspeech amplitude-modulated noises modeled these patterns of enhancement, identification of the noises as Mandarin lexical tone categories was more accurate than identification of noises modeling phonated speech amplitude and duration cues. Thus, speakers exaggerate secondary cues in whispered speech and listeners make use of this information. Yet, enhancement is not symmetric among the four Mandarin lexical tones, indicating possible constraints on the realization of this enhancement.