Alejna Brugos

Turning points, tonal targets, and the English L- phrase accent

This study of the alignment of L- in the H* L- H% contour of American English finds the strongest predictor of the location of the retracted phrase-accent “elbow” to be the location of the accent-related F0 peak, rather than one of a set of metrical “attractors” investigated. A strong correlation between peak height and elbow sharpness suggests that the elbow may arise from interaction between peak height and perception-based constraints on the implementation of postnuclear deaccenting: F0 must become low immediately after the Nuclear-Pitch-Accented syllable, to prevent the percept of a pitch accent on a following accentable syllable. Relativised Area Under the Curve (R-AUC), a global measure for characterising F0 contours, distinguishes this H* L- from contrasting contours (e.g., H* L*) more reliably than a turning point-based approach focused on the location/scaling of an F0 elbow. The R-AUC measure is sensitive to perceptually significant, but difficult-to-quantify, changes in contour shape, while avoiding the pitfalls of purely shape-based theories.

On the nature of perceptual differences between accentual peaks and plateaux

It is probably not much of an overstatement to say that the theoretical mainstream in intonational phonology today takes the historical debate between level-based and configuration-based approaches to intonation to be resolved in such a way that explicit reference to contour shape no longer has any place in phonological representations. Part of what has made this an attractive position is the high degree of within-category variability one encounters in the shapes of phonological entities such as pitch accents in phonetic realization. It is well-known, for example, that a given pitch accent category (e.g., English L+H*, as shown in Figure 1) can be realized either as a sharp peak (as on the left), or instead can linger for a time near the F0 maximum, creating what is often referred to as a plateau-shaped configuration (as on the right). This distinction is not known to form the basis of a phonological contrast in any intonation system, nor is it clear whether the distinction is categorical, or even whether it is conditioned by contextual factors.

Alternatives to f0 turning points in American English intonation.

Since the inception of the autosegmental‐metrical approach to intonation (Bruce 1977, Pierrehumbert 1980, Ladd 1996), the location and scaling of f0 turning points have been used to characterize phonologically distinct f0 contours in various languages, including American English. This approach is undermined, however, by the difficulty listeners experience in perceiving differences in turning point location. Numerous studies have demonstrated either listener insensitivity to changes in turning point location or the capacity for other aspects of contour “shape” to override turning‐point alignment for contour identification (Chen 2003, D’Imperio 2000, Niebuhr 2008). Even labelers with access to visual representations of the f0 encounter similar challenges. By contrast, a family of related measurements using area under the f0 curve to quantify differences in contour shape appear more robust. For example, a measure of the synchronization of the center of gravity of the accentual rise with the boundaries of the...

A range of intonation patterns produced in an elicitation task

A production task was designed to elicit a specific intonation contour, characterized by an exaggerated rise‐fall‐rise in f0 (L+H*L−H% in ToBI terms), conveying an attitude of ‘‘dismayed surprise.’’ Speakers were given models, a short practice period, and a preceding context for each utterance. A targetlike rise‐fall‐rise contour (including H*L−H% variants) was successfully elicited for each of the contexts, but in less than half the utterances: Of 1134 utterances, 631 (56%) were judged by a panel of 3 experienced ToBI labelers as different from the intended contour, e.g., L*H−H%. Of these, 261 were produced with contours perceptually similar to the target, with a sustained flat or minimally rising f0 after the fall from the pitch accent, or with the rise occurring early in the next phrase. Alignment characteristics and individual speaker data may determine whether these are one contour with a continuum of realizations, or separate contours. These results (a) suggest that speakers have more than one way o...

Dynamic pitch and pitch range interact in distortions of perceived duration of American English speech tokens

Previous research showed that pitch factors can distort perceived duration: tokens with dynamic or higher f0 tend to be perceived as longer than comparable level-f0 or lower-f0 tokens, and silent intervals bounded by tokens of widely differing pitch are heard as longer than those bounded by tokens closer in pitch (the kappa effect). Fourteen subjects were asked to judge which of two exemplars of a spoken word sounded longer. All tokens were created from the same base file with manipulations of objective duration, f0 contour (plateaux vs. rises of different slopes) and pitch range. Results show that pitch range relation between the two exemplars was a stronger predictor of perceived duration distortion than f0 contour. In addition to previously demonstrated effects of f0 height (Yu, 2010), greater f0 discontinuity between tokens increases the likelihood that the first token of a pair will be judged as longer, suggesting that some previous findings showing the effects of dynamic pitch on perceived duration ...

Individual differences in the perception of fundamental frequency scaling in American English speech

Although most participants (N = 62) in an F0 scaling experiment judged open syllables (day) as higher in pitch than closed syllable tokens (dane, dave) with the same F0 contour, a subset did not. Results indicate that, in general, listeners perceptually discount F0 over coda regions when judging overall F0 level, and the degree of discount is related to the (lack of) sonority in the coda: day tokens are judged significantly higher than dane tokens which are judged significantly higher than dave tokens with the same F0 contour (dane-dave p < 0.001, dane-day p < 0.01). However, individual differences are observed: ten listeners showed no significant differences in the perception of F0 levels between the three types of tokens. On the other hand, a contrasting subset of ten subjects demonstrated highly significant differences (p< 0.001). The remaining 42 subjects behaved similarly to the entire subject pool with only slightly less significant differences between dane and day F0 level judgments (p < 0.05). Therefore, for about 16% of subjects, the F0 over the coda is not discounted in judging F0 level. These individual responses in F0 scaling perception mirror differences found in the Frequency Following Response (e.g., [1]) and could indicate individual differences in F0 processing.

F0 peaks aligned with nonprominent syllables in American English

The occurrence of F0 peaks on nonprominent syllables in American English (e.g., ‐ing or a‐ in reading again) raises the question of how to label these inflection points. This pattern is not infrequent, as shown by samples from two prosodically labeled corpora of natural speech (ToBI labeled MIT Maptask and BU FM Radio News). The Maptask sample from a single speaker (235 seconds, 520 words) contained 46 H* !H* sequences; 19 had an F0 peak on a weak syllable between the two accented syllables. Individual speakers vary in their use of this pattern: for 3 Radio News speakers reading the same paragraph, each speaker produced 11 H* !H* sequences of which 6, 1, and 5, respectively, showed the non‐accent‐aligned peak. Informal listening as well as experiments described by Dilley (2004) suggest that alignment of the F0 peak with different nonprominent syllables between the two accents can change the perceived relative prominences of the accents, but current ToBI labels do not specify this alignment. Because F0 inf...