Björn Lindblom

Explaining Phonetic Variation: A Sketch of the H&H Theory

The H&H theory is developed from evidence showing that speaking and listening are shaped by biologically general processes. Speech production is adaptive. Speakers can, and typically do, tune their performance according to communicative and situational demands, controlling the interplay between production-oriented factors on the one hand, and output-oriented constraints on the other. For the ideal speaker, H&H claims that such adaptations reflect his tacit awareness of the listener’s access to sources of information independent of the signal and his judgement of the short-term demands for explicit signal information. Hence speakers are expected to vary their output along a continuum of hyper- and hypospeech. The theory suggests that the lack of invariance that speech signals commonly exhibit (Perkell and Klatt 1986) is a direct consequence of this adaptive organization (cf MacNeilage 1970). Accordingly, in the H&H program the quest for phonetic invariance is replaced by another research task: Explicating the notion of sufficient discriminability and defining the class of speech signals that meet that criterion.

Spectrographic Study of Vowel Reduction

Measurements of formant frequencies and duration are reported for 8 Swedish vowels uttered by a male talker in three consonantal environments under varying timing conditions. An exponential function is used to describe the extent to which formant frequencies in the vowels reach their target values as a function of vowel‐segment duration. A target is specified by the asymptotic values of the first two formant frequencies of the vowel and is independent of consonantal context and duration. It is thus an invariant attribute of the vowel. The results suggest an interpretation in terms of a simple dynamic model of vowel articulation.

Interaction between duration, context, and speaking style in English stressed vowels

Acoustic observations are reported for English front vowels embedded in a /w—l/ frame and carrying constant main stress. The vowels were produced by five speakers in clear and citation‐form styles at varying durations but at a constant speaking rate. The acoustic analyses revealed (i) that formant patterns were systematically displaced in the direction of the frequencies of the consonants of the adjacent pseudosymmetrical context; (ii) that those displacements depended in a lawful manner on vowel duration; (iii) that this context and duration dependence was more limited for clear than for citation‐form speech, and that the smaller formant shifts of clear speech tended to be achieved by increases in the rate of formant frequency change. The findings are compatible with a revised, and biomechanically motivated, version of the vowel undershoot model [Lindblom, J. Acoust. Soc. Am. 35, 1773–1781 (1963)] that derives formant patterns from numerical information on three variables: The ‘‘locus‐target’’ distance, ...

Acoustical Consequences of Lip, Tongue, Jaw, and Larynx Movement

In the past, numerous attempts have been made to develop quantitative models of the human vocal tract. The present paper describes such a model and some of its acoustic properties. It has been constructed with a view towards finding a set of parameters that are physiologically “natural.” Thus it differs from earlier schemes in that the mandible has been incorporated as an independent parameter. Other novel features can be interpreted to represent larynx height, the rounding‐spreading action of the lip musculature, and “genioglossal,” “styloglossal,” and “hyoglossal” components of tongue shape. The paper describes the acoustic effects of varying these parameters systematically. The model is capable of generating most of the vowel qualities known to occur in the languages of the world. In general, well‐known vowel sounds are found along the extreme contours of the total acoustic space characteristic of the model. They are not necessarily located at acoustic “plateaus” or regions insensitive to articulatory ...

Economy of Speech Gestures

Normal language acquisition and adult verbal behavior presuppose speech production. This fact makes it reasonable to assume that languages tend to evolve sound patterns that can be seen as adaptations to biological constraints of speech production. This reasoning seems valid also for speech perception and speech development, which presumably introduce their own boundary conditions on linguistic form. The constraints of speaking, listening, and learning thus interact in complex ways to delimit humanly possible sound patterns.

Formant frequencies of some fixed‐mandible vowels and a model of speech motor programming by predictive simulation

Formant frequency data are reported for Swedish vowels produced both with fixed and unconstrained mandible. Measurements were made at the first glottal pulse to confine interpretation of the results to nonauditory feedback mechanisms. Results indicated that in spite of physiologically unnatural jaw openings, subjects were able to produce F patterns within the ranges of variation of the normal vowels. Results are explained by hypothesizing that the “instantaneous” learning of highly unfamiliar tasks, such as compensatory articulation of fixed‐mandible vowels, is possible because normal speech motor programming is indeed “compensatory” rather than due to either speakers drawing upon past similar experience or invoking special motor mechanisms distinct from those of natural speech. That is, it operates in a context‐sensitive mode to achieve listener‐oriented goals. Since “contexts” constitutes an essentially infinite class of events the programming must be “creative,” or capable of handling conditions never before experienced. A model of speech production is proposed that achieves increased plasticity of motor control by incorporating an “upstairs” predictive component used to simulate “downstairs” processes of execution.

On the Rôle of Formant Transitions in Vowel Recognition

An inventory of speechlike sounds was synthesized displaying systematic variations of the rate and direction of formant transitions. These sounds were specified by a set of vowel formant patterns selected along a continuum varying from [U] to [I] they were assigned to isolated, steady‐state vowels, and to the points of zero rate of formant frequency change in symmetrical consonant‐vowel‐consonant syllables. The time variations of formant frequencies were made convex and concave by the choice of two consonantal frames: [w‐w] and [j‐j]. The results obtained in a series of vowel identification experiments indicate that a listeners categorization of the continuum varied as a function of the environment and the duration of the vowel. These findings suggest that, in the recognition of monosyllabic nonsense speech, the identity of a vowel is determined not solely by the formant‐frequency pattern at the point of closest approach to target, but also by the direction and rate of adjacent formant transitions. In ge...

Production of bite‐block vowels: Acoustic equivalence by selective compensation

Acoustic and articulatory data are reported for steady state vowels produced both normally and with a bite block. The formant patterns of the bite block vowels were found to approximate those of the naturally spoken vowels. Measurements derived from lateral view still x‐ray films showed that the bite blocks induce drastic articulatory reorganization. Using a mandibular frame of reference, we found that speakers compensated for a large bite block by using supershapes of the tongue and the lips (for /u/ and /o/). Comparing the two productions using a maxillary frame of reference, we noted that compensation was maximum at the points of maximum constriction and incomplete or partial at points of vocal tract expansion. A computer simulation of our speakers compensatory strategy revealed that they behaved optimally according to acoustic theory. These findings suggest that a vowel target is coded neurophysiologically in terms of acoustically significant area function information, specifically, by information rel...

On the Role of Perception in Shaping Phonological Assimilation Rules

Assimilation of nasals to the place of articulation of following consonants is a common and natural process among the worlds languages. Recent phonological theory attributes this naturalness to the postulated geometry of articulatory features and the notion of spreading (McCarthy, 1988). Others view assimilation as a result of perception (Ohala, 1990), or as perceptually tolerated articulatory simplification (Kohler, 1990). Kohler notes that certain consonant classes (such as nasals and stops) are more likely than other classes (such as fricatives) to undergo place assimilation to a following consonant. To explain this pattern, he proposes that assimilation tends not to occur when the members of a consonant class are relatively distinctive perceptually, such that their articulatory reduction would be particularly salient. This explanation, of course, presupposes that the stops and nasals which undergo place assimilation are less distinctive than fricatives, which tend not to assimilate. We report experimental results that confirm Kohlers perceptual assumption: In the context of a following word initial stop, fricatives were less confusable than nasals or unreleased stops. We conclude, in agreement with Ohala and Kohler, that perceptual factors are likely to shape phonological assimilation rules.

Generative theories in language and music descriptions

The style of a set of Swedish nursery tunes is described in terms of a generative rule system. A generative rule system producing melodically similar versions of an old Swedish folk song is also presented. Examples of melodies generated by these two rule systems are given. Both these rule systems are similar in several respects. Thus, the marking of the hierarchical constituent structure seerns to be one of the important principles in composing simple melodies. The rule systems also show a number of similarities with the Chomsky & Halle (1968) generative phonology of English. For instance, the procedures used for deriving a stress contour from a tree diagram are almost identical. Moreover, in sentences as in melodies this stress, or prominence contour is of decisive importance to the generation of the surface structure, such as meter, harmony, and sequences of pitches. It is believed that such parallels between language and music reflect characteristics of man s perceptual and cognitive capacities.