Marc Garellek

Explaining sonority projection effects

The term sonority projection refers to behavioural distinctions speakers make between unattested phonological sequences on the basis of sonority. For example, among onset clusters, the well-formedness relation [bn]>[lb] is observed in speech perception, speech production and non-word acceptability (Davidson 2006 , 2007 , Berent et al. 2007 , Albright, ms). We begin by replicating the sonority projection effects in a non-word acceptability study. Then we evaluate the extent to which sonority projection is predicted by existing computational models of phonotactics (Coleman & Pierrehumbert 1997 , Hayes & Wilson 2008 , inter alia ). We show that a model based only on lexical statistics can explain sonority projection in English without a pre-existing sonority sequencing principle. To do this, a model must possess (i) a featural system supporting sonority-based generalisations, and (ii) a context representation including syllabification or equivalent information.

The acoustic consequences of phonation and tone interactions in Jalapa Mazatec

San Felipe Jalapa de Diaz (Jalapa) Mazatec is unusual in possessing a three-way phonation contrast and three-way level tone contrast independent of phonation. This study investigates the acoustics of how phonation and tone interact in this language, and how such interactions are maintained across variables like speaker sex, vowel timecourse, and presence of aspiration in the onset. Using a large number of words from the recordings of Mazatec made by Paul Kirk and Peter Ladefoged in the 1980s and 1990s, the results of our acoustic and statistical analysis support the claim that spectral measures like H1-H2 and mid-range spectral measures like H1-A2 best distinguish each phonation type, though other measures like Cespstral Peak Prominence are important as well. This is true regardless of tone and speaker sex. The phonation contrasts are strongest in the first third of the vowel and then weaken towards the end. Although tones remain distinct from one another in terms of F0 throughout the vowel, for laryngealized phonation the tone contrast in F0 is partially lost in the initial third. This study shows that the complex orthogonal three-way phonation and tone contrasts do remain acoustically distinct according to the measures studied, despite partial neutralizations in any given measure.

Voice quality and tone identification in White Hmong

This study investigates the importance of source spectrum slopes in the perception of phonation by White Hmong listeners. In White Hmong, nonmodal phonation (breathy or creaky voice) accompanies certain lexical tones, but its importance in tonal contrasts is unclear. In this study, native listeners participated in two perceptual tasks, in which they were asked to identify the word they heard. In the first task, participants heard natural stimuli with manipulated F0 and duration (phonation unchanged). Results indicate that phonation is important in identifying the breathy tone, but not the creaky tone. Thus, breathiness can be viewed as contrastive in White Hmong. Next, to understand which parts of the source spectrum listeners use to perceive contrastive breathy phonation, source spectrum slopes were manipulated in the second task to create stimuli ranging from modal to breathy sounding, with F0 held constant. Results indicate that changes in H1-H2 (difference in amplitude between the first and second harmonics) and H2-H4 (difference in amplitude between the second and fourth harmonics) are independently important for distinguishing breathy from modal phonation, consistent with the view that the percept of breathiness is influenced by a steep drop in harmonic energy in the lower frequencies.

Voice quality strengthening and glottalization

Abstract Prominence and phrase-initial position strongly favor the presence of word-initial glottalization in English and other languages. This suggests that word-initial glottalization may arise from prosodic strengthening – the phenomenon by which sounds are more ‘strongly’ articulated in stronger prosodic positions. However, if word-initial glottalization is due to prosodic strengthening, what exactly is being strengthened? The goal of this study is to determine whether voice quality is strengthened in vowels and sonorants, and whether this type of strengthening is consistent with word-initial glottalization. Prominent and/or phrase-initial voicing in English and Spanish was analyzed articulatorily using electroglottography. The results reveal that voicing during word-initial vowels in English and Spanish has increased contact under prominence, but not at phrasal onsets. Non-prominent initial vowels and sonorants are characterized by a decrease in contact, which I argue is inconsistent with both word-initial glottalization and voice quality strengthening. Based on the results, a prominence-driven account of word-initial glottalization is proposed and motivated.

The timing and sequencing of coarticulated non-modal phonation in English and White Hmong

Despite the growing number of studies on the acoustics of non-modal phonation, little is known about how two distinct non-modal phonations can interact acoustically when coarticulated. This study investigates the acoustics of breathy-to-creaky phonation contours in vowels from a production study of native speakers of English and White Hmong. These languages differ in the nature of the non-modal phonation types. In the English corpus, both the breathiness and creakiness are non-contrastive. In the Hmong corpus, the breathiness can be contrastive or a result of coarticulation with a neighboring segment, but the creakiness is always contrastive. The contours were analyzed using the three measures of phonation that were found to best differentiate non-modal from modal phonation in these languages: H1 n –H2 n ,H 1 n –A1 n , and harmonicsto-noise ratio. Results from these measures provide support for the presence of breathy–creaky contours in vowels. The timing and sequencing of the breathy and creaky phonation types are largely dependent on whether they are contrastive, with contrastive non-modal phonation being present during more portions of the vowel than non-modal phonation derived from coarticulation. The acoustic results also provide evidence for simultaneous breathy and creaky phonation types in Hmong.

Perceptual importance of the voice source spectrum from H2 to 2 kHz

Modeling the source spectrum requires understanding of the perceptual importance of different spectral-domain attributes of the voice source. Although the roles of H1-H2 and high-frequency harmonics in quality perception are somewhat understood, the extent of spectral detail that is perceptually significant in other frequency ranges is not known. This experiment examined the perceptual importance of amplitude difference between the second and fourth harmonics (H2-H4), which varies with linguistically significant changes in mode of phonation and pitch. To further determine if sensitivity depends on H1-H2 or on F0, we synthesized non-pathological male (F0=100 Hz) and female voices (F0 = 200 Hz) and manipulated the values of H2-H4 by 1 dB increments over a 20 dB range, for three different H1-H2 levels. Listeners heard pairs of stimuli in a 1-up, 2-down adaptive paradigm, and variations in just-noticeable-difference for H2-H4 as a function of F0 and H1-H2 were assessed with analysis of variance (ANOVA). Discu...

Modeling the voice source in terms of spectral slopes.

A psychoacoustic model of the voice source spectrum is proposed. The model is characterized by four spectral slope parameters: the difference in amplitude between the first two harmonics (H1-H2), the second and fourth harmonics (H2-H4), the fourth harmonic and the harmonic nearest 2 kHz in frequency (H4-2 kHz), and the harmonic nearest 2 kHz and that nearest 5 kHz (2 kHz-5 kHz). As a step toward model validation, experiments were conducted to establish the acoustic and perceptual independence of these parameters. In experiment 1, the model was fit to a large number of voice sources. Results showed that parameters are predictable from one another, but that these relationships are due to overall spectral roll-off. Two additional experiments addressed the perceptual independence of the source parameters. Listener sensitivity to H1-H2, H2-H4, and H4-2 kHz did not change as a function of the slope of an adjacent component, suggesting that sensitivity to these components is robust. Listener sensitivity to changes in spectral slope from 2 kHz to 5 kHz depended on complex interactions between spectral slope, spectral noise levels, and H4-2 kHz. It is concluded that the four parameters represent non-redundant acoustic and perceptual aspects of voice quality.

Perceptual evaluation of voice source models.

Models of the voice source differ in their fits to natural voices, but it is unclear which differences in fit are perceptually salient. This study examined the relationship between the fit of five voice source models to 40 natural voices, and the degree of perceptual match among stimuli synthesized with each of the modeled sources. Listeners completed a visual sort-and-rate task to compare versions of each voice created with the different source models, and the results were analyzed using multidimensional scaling. Neither fits to pulse shapes nor fits to landmark points on the pulses predicted observed differences in quality. Further, the source models fit the opening phase of the glottal pulses better than they fit the closing phase, but at the same time similarity in quality was better predicted by the timing and amplitude of the negative peak of the flow derivative (part of the closing phase) than by the timing and/or amplitude of peak glottal opening. Results indicate that simply knowing how (or how well) a particular source model fits or does not fit a target source pulse in the time domain provides little insight into what aspects of the voice source are important to listeners.

Toward a unified theory of voice production and perception

At present, two important questions about voice remain unanswered: When voice quality changes, what physiological alteration caused this change, and if a change to the voice production system occurs, what change in perceived quality can be expected? We argue that these questions can only be answered by an integrated model of voice linking production and perception, and we describe steps towards the development of such a model. Preliminary evidence in support of this approach is also presented. We conclude that development of such a model should be a priority for scientists interested in voice, to explain what physical condition(s) might underlie a given voice quality, or what voice quality might result from a specific physical configuration.

Breathy voice during nasality: A cross-linguistic study

Abstract In some languages, there is a diachronic correspondence between nasal and breathy sounds, whose origin is often attributed to the acoustic similarities between nasal and breathy vowels. In this study, we test whether nasal consonants and vowels are also produced with breathier voice quality than their oral counterparts in three Yi (Loloish) languages: Bo, Luchun Hani, and Southern Yi. We analyzed oral vs. nasal vowels and consonants using electroglottographic and acoustic measures of phonation. Results indicate that nasal consonants are often breathier than laterals, as are vowels following nasals when compared to vowels following oral consonants. These findings support the assumption that at least some of these nasal-breathy sound changes involve a stage in which the two articulations co-occur. We claim that the production of breathy voice quality during nasals can arise through listener misperception or phonetic enhancement. These findings also contribute to the understanding of nasality as an abstract feature that involves multiple articulations.