Mary E. Beckman

The articulatory kinematics of final lengthening

In order to understand better the phonetic control of final lengthening, the articulation of phrase-final syllables was compared with that of two other contexts known to increase syllable duration: accent and slow tempo. The kinematics of jaw movements in [pap] sequences and of lower lip movements in [pe] sequences for four subjects were interpreted in terms of a task-dynamic model. There was evidence of two different control strategies: decreasing intragestural stiffness to slow down some part of the syllable, and changing intergestural phasing to decrease overlap of the vowel gesture by the consonant. The first was used in slowing down tempo, whereas the second was used to increase the duration of accented syllables over unaccented syllables. Both strategies were implicated in phrase-final lengthening. In accented syllables, final closing gestures generally were longer and slower, but not more displaced. The two slowest subjects, however, used the other strategy in their slow-tempo final syllables. Final lengthening in reduced syllables was more difficult to interpret. The relationship between peak velocity and displacement suggested that a lesser stiffness is obscured by an increased gestural amplitude. Thus, by comparison to lengthening for accent, final lengthening is like a localized change in speaking tempo, although it cannot be equated directly with the specification of stiffness.

The Parsing of Prosody

Prosody has been demonstrated to play some role in parsing the grammatica l structure of utterances of texts that might otherwise display surface (syntactic) ambiguity. In the context of this research, it is important to be able to state with reasonable certainty what the prosody of an utterance is. This paper considers the fact that the prosody is itself a grammatical (phonological) structure that must be parsed. First, prosodic categories that determine or are marked by the intonational pattern are described for English and Japanese, concentrating on the categories “pitch accent” and tonally marked “phrases” at levels of the prosodic hierarchy above the (prosodic) word. Then various potential ambiguities in parsing these categories are discussed, with attention to both the phonological and the phonetic contexts which are most conducive to ambiguity between alternative prosodic parses, and to the implications of these ambiguities for claims about the relationship between prosody and syntax.

Contrast and covert contrast: The phonetic development of voiceless sibilant fricatives in English and Japanese toddlers

This paper examines the acoustic characteristics of voiceless sibilant fricatives in English-and Japanese-speaking adults and the acquisition of contrasts involving these sounds in 2- and 3-year-old children. Both English and Japanese have a two-way contrast between an alveolar fricative (/s/), and a postalveolar fricative (/∫/ in English and /ɕ/ in Japanese). Acoustic analysis of the adult productions revealed cross-linguistic differences in what acoustic parameters were used to differentiate the two fricatives in the two languages and in how well the two fricatives were differentiated by the acoustic parameters that were investigated. For the childrens data, the transcription results showed that English-speaking children generally produced the alveolar fricative more accurately than the postalveolar one, whereas the opposite was true for Japanese-speaking children. In addition, acoustic analysis revealed the presence of covert contrast in the productions of some English-speaking and some Japanese-speaking children. The different development patterns are discussed in terms of the differences in the fine phonetic detail of the contrast in the two languages.

The interplay between prosodic structure and coarticulation

In this paper we draw on a linguistic model of prosodic structure and a task-dynamic model of speech gestures to account for the interplay of coarticulation and stress in English. We reinterpret results from two experiments in which articulator movements were recorded for utterances varying in pitch accent placement. In the first experiment, jaw kinematics were studied in post-nuclear unaccented and nuclear accented [pap] syllables. The kinematic patterns suggested that gestures in syllables with greater stress (nuclear accented) show less coarticulatory overlap. By contrast, the vowels low jaw target is undershot in unaccented syllables. Two hypotheses are possible. Either the jaw is lower in stressed syllables so more energy can radiate from the mouth (“sonority expansion”) or the jaw is lower to help distinguish the low vowel from other vowels (“hyperarticulation”). Another experiment differentiates the two hypotheses by examining tongue point positions in [put] preceding a [Ö]. In the more stressed syllables, the tongue dorsum retracts more, likely to make a more distinct back vowel. Also, the amount of assimilation of the alveolar stop to the following dental is reduced. Both results suggest hyperarticulation rather than sonority expansion. Thus, it seems that coarticulation is reduced in stressed syllables, because stressed syllables are hyperarticulated.

The Ontogeny of Phonological Categories and the Primacy of Lexical Learning in Linguistic Development.

In this paper, we draw on recent developments in several areas of cognitive science that suggest that the lexicon is at the core of grammatical generalizations at several different levels of representation. Evidence comes from many sources, including recent studies on language processing in adults and on language acquisition in children. Phonological behavior is influenced very early by pattern frequency in the lexicon of the ambient language, and we propose that phonological acquisition might provide the initial bootstrapping into grammatical generalization in general. The phonological categories over which pattern frequencies are calculated, however, are neither transparently available in the audiovisual signal nor deterministically fixed by the physiological and perceptual capacities of the species. Therefore, we need several age-appropriate models of how the lexicon can influence a childs interactions with the ambient language over the course of phonological acquisition.

Segment duration and the mora in Japanese

Linguists have made various claims for the mora as a durational unit in Japanese. One of the strongest of these claims is that the mora has such a basic phonetic reality that, for example, vowel lengths are adjusted to compensate for the intrinsic durations of tautomoraic consonants [M. S. Han, Onsei no kenkyuu 10, 81–100 (1962)]. Examination of a preliminary corpus of utterances used in the development of synthesis rules for Japanese, however, did not reveal this tendency toward moraic isochrony. This discrepancy between our findings and previous claims has led us to examine segment durations in a larger set of utterances (including readings by several native speakers of a long narrative passage) in order to determine whether a tendency to equalize mora durations might become apparent after other factors influencing duration are accounted for.

Automatic ToBI prediction and alignment to speed manual labeling of prosody

Tagging of corpora for useful linguistic categories can be a time-consuming process, especially with linguistic categories for which annotation standards are relatively new, such as discourse segment boundaries or the intonational events marked in the Tones and Break Indices (ToBI) system for American English. A ToBI prosodic labeling of speech typically takes even experienced labelers from 100 to 200 times real time. An experiment was conducted to determine (1) whether manual correction of automatically assigned ToBI labels would speed labeling, and (2) whether default labels introduced any bias in label assignment. A large speech corpus of one female speaker reading several types of texts was automatically assigned default labels. Default accent placement and phrase boundary location were predicted from text using machine learning techniques. The most common ToBI labels were assigned to these locations for default tones and break type. Predicted pitch accents were automatically aligned to the mid-point of the word, while breaks and edge tones were aligned to the end of the phrase-final word. The corpus was then labeled by a group of five trained transcribers working over a period of nine months. Half of each set of recordings was labeled in the standard fashion without default labels, and the other half was presented with preassigned default labels for labelers to correct. Results indicate that labeling from defaults was generally faster than standard labeling, and that defaults had relatively little impact on label assignment.

Segment Duration and the ‘Mora’ in Japanese

An experiment was conducted to test two predictions entailed by the hypothesis that Japanese morae have constant durations. The first prediction is that a segment’s duration will conform to its moraic

Articulatory Timing and the Prosodic Interpretation of Syllable Duration

A number of different prosodic effects (e. g. intonation-phrase-final position, the presence of stress or accent) increase syllable duration, as conventionally measured by the spacing of abrupt energy transitions in the acoustic signal. However, different prosodic contrasts may have different influences on syllable-internal articulatory organization. The present study examined the time course of vowel-related opening and closing mandibular gestures in four different prosodic contexts. For some prosodic effects, such as intonation-phrase-final lengthening, longer acoustic durations were associated with a disproportionate lengthening of the latter part of the vocalic gesture. By contrast, the presence of nuclear stress was associated with a more even distribution of lengthening throughout the syllable. These results suggest that the rhythmic effects of different prosodic contrasts cannot be adequately modelled in terms of millisecond values or durational ratios for acoustic segments. It is proposed that a suitable phonological representation of the rhythms of stress and phrasing might describe them as the time course of a syllable’s phonetic sonority.

Some Cross-Linguistic Evidence for Modulation of Implicational Universals by Language-Specific Frequency Effects in Phonological Development

Although broad-focus comparisons of consonant inventories across children acquiring different languages can suggest that phonological development follows a universal sequence, finer-grained statistical comparisons can reveal systematic differences. This cross-linguistic study of word-initial lingual obstruents examined some effects of language-specific frequencies on consonant mastery. Repetitions of real words were elicited from 2- and 3-year-old children who were monolingual speakers of English, Cantonese, Greek, or Japanese. The repetitions were recorded and transcribed by an adult native speaker for each language. Results found support for both language-universal effects in phonological acquisition and for language-specific influences related to phoneme and phoneme sequence frequency. These results suggest that acquisition patterns that are common across languages arise in two ways. One influence is direct, via the universal constraints imposed by the physiology and physics of speech production and perception, and how these predict which contrasts will be easy and which will be difficult for the child to learn to control. The other influence is indirect, via the way universal principles of ease of perception and production tend to influence the lexicons of many languages through commonly attested sound changes.