Allard Jongman

Acoustic characteristics of English fricatives

This study constitutes a large-scale comparative analysis of acoustic cues for classification of place of articulation in fricatives. To date, no single metric has been found to classify fricative place of articulation with a high degree of accuracy. This study presents spectral, amplitudinal, and temporal measurements that involve both static properties (spectral peak location, spectral moments, noise duration, normalized amplitude, and F2 onset frequency) and dynamic properties (relative amplitude and locus equations). While all cues (except locus equations) consistently serve to distinguish sibilant from nonsibilant fricatives, the present results indicate that spectral peak location, spectral moments, and both normalized and relative amplitude serve to distinguish all four places of fricative articulation. These findings suggest that these static and dynamic acoustic properties can provide robust and unique information about all four places of articulation, despite variation in speaker, vowel context, and voicing.

Processing of English inflectional morphology

The present paper explores the representation of inflectional morphology in the English lexicon. There has been a long-standing debate about how these inflectional relationships might be involved during on-line processing. Inflected forms may be derived from an uninflected base form by rule application; by contrast, both regular and irregular inflection may be treated in the same way, with morphological patterns emerging from mappings between base and inflected forms. The present series of experiments investigated these issues using a lexical decision task. The first experiment showed that response latencies to nouns were significantly shorter than those to verbs. A possible explanation for these results can be found in differences in inflectional structure between English nouns and verbs. Namely, the relative frequency of uninflected compared with inflected forms is greater for nouns than for verbs. Two additional experiments compared noun stimuli with different inflectional structures. In all cases, differences in response latencies were predicted by the frequency of the surface form, whether uninflected or inflected. The pattern of results lends support for a unitary associative system for processing regular inflection of nouns in English and argues against the view that regular inflected plurals are derived by rule from a single, uninflected lexical entry.

fMRI Evidence for Cortical Modification during Learning of Mandarin Lexical Tone

Functional magnetic resonance imaging was employed before and after six native English speakers completed lexical tone training as part of a program to learn Mandarin as a second language. Language-related areas including Brocas area, Wernickes area, auditory cortex, and supplementary motor regions were active in all subjects before and after training and did not vary in average location. Across all subjects, improvements in performance were associated with an increase in the spatial extent of activation in left superior temporal gyrus (Brodmanns area 22, putative Wernickes area), the emergence of activity in adjacent Brodmanns area 42, and the emergence of activity in right inferior frontal gyrus (Brodmanns area 44), a homologue of putative Brocas area. These findings demonstrate a form of enrichment plasticity in which the early cortical effects of learning a tone-based second language involve both expansion of preexisting language-related areas and recruitment of additional cortical regions specialized for functions similar to the new language functions.

Incomplete neutralization and other sub-phonemic durational differences in production and perception: Evidence from Dutch

Abstract Words which are expected to contain the same surface string of segments may, under identical prosodic circumstances, sometimes be realized with slight differences in duration. Some researchers have attributed such effects to differences in the words’ underlying forms (incomplete neutralization), while others have suggested orthographic influence and extremely careful speech as the cause. In this paper, we demonstrate such sub-phonemic durational differences in Dutch, a language which some past research has found not to have such effects. Past literature has also shown that listeners can often make use of incomplete neutralization to distinguish apparent homophones. We extend perceptual investigations of this topic, and show that listeners can perceive even durational differences which are not consistently observed in production. We further show that a difference which is primarily orthographic rather than underlying can also create such durational differences. We conclude that a wide variety of factors, in addition to underlying form, can induce speakers to produce slight durational differences which listeners can also use in perception.

What information is necessary for speech categorization? Harnessing variability in the speech signal by integrating cues computed relative to expectations.

Most theories of categorization emphasize how continuous perceptual information is mapped to categories. However, equally important are the informational assumptions of a model, the type of information subserving this mapping. This is crucial in speech perception where the signal is variable and context dependent. This study assessed the informational assumptions of several models of speech categorization, in particular, the number of cues that are the basis of categorization and whether these cues represent the input veridically or have undergone compensation. We collected a corpus of 2,880 fricative productions (Jongman, Wayland, & Wong, 2000) spanning many talker and vowel contexts and measured 24 cues for each. A subset was also presented to listeners in an 8AFC phoneme categorization task. We then trained a common classification model based on logistic regression to categorize the fricative from the cue values and manipulated the information in the training set to contrast (a) models based on a small number of invariant cues, (b) models using all cues without compensation, and (c) models in which cues underwent compensation for contextual factors. Compensation was modeled by computing cues relative to expectations (C-CuRE), a new approach to compensation that preserves fine-grained detail in the signal. Only the compensation model achieved a similar accuracy to listeners and showed the same effects of context. Thus, even simple categorization metrics can overcome the variability in speech when sufficient information is available and compensation schemes like C-CuRE are employed.

Dichotic Perception of Mandarin Tones by Chinese and American Listeners

The dichotic perception of Mandarin tones by native and nonnative listeners was examined in order to investigate the lateralization of lexical tone. Twenty American listeners with no tone language background and 20 Chinese listeners were asked to identify dichotically presented tone pairs by identifying which tone they heard in each ear. For the Chinese listeners, 57% of the total errors occurred via the left ear, indicating a significant right ear advantage. However, the American listeners revealed no significant ear preference, with 48% of the errors attributable to the left ear. These results indicated that Mandarin tones are predominantly processed in the left hemisphere by native Mandarin speakers, whereas they are bilaterally processed by American English speakers with no prior tone experience. The results also suggest that the left hemisphere superiority for native Mandarin tone processing is similar to native processing of other tone languages.

Acoustic characteristics of clearly spoken English fricatives

Speakers can adopt a speaking style that allows them to be understood more easily in difficult communication situations, but few studies have examined the acoustic properties of clearly produced consonants in detail. This study attempts to characterize the adaptations in the clear production of American English fricatives in a carefully controlled range of communication situations. Ten female and ten male talkers produced fricatives in vowel-fricative-vowel contexts in both a conversational and a clear style that was elicited by means of simulated recognition errors in feedback received from an interactive computer program. Acoustic measurements were taken for spectral, amplitudinal, and temporal properties known to influence fricative recognition. Results illustrate that (1) there were consistent overall style effects, several of which (consonant duration, spectral peak frequency, and spectral moments) were consistent with previous findings and a few (notably consonant-to-vowel intensity ratio) of which were not; (2) specific acoustic modifications in clear productions of fricatives were influenced by the nature of the recognition errors that prompted the productions and were consistent with efforts to emphasize potentially misperceived contrasts both within the English fricative inventory and based on feedback from the simulated listener; and (3) talkers differed widely in the types and magnitude of all modifications.

Acoustic correlates of breathy and clear vowels: the case of Khmer

Abstract This study investigates acoustic correlates of the putative breathy and clear phonation type contrast in a dialect of Khmer (Cambodian) spoken in Chanthaburi Province, Thailand. The goal is to determine whether this Khmer dialect still preserves this historical contrast. Out of seven acoustic parameters measured, four, namely * H 1 − * H 2 , * H 1 −A 1 , * H 1 − * A 3 , and vowel RMS amplitude successfully distinguished between breathy and clear vowels, with * H 1 − * H 2 measured at the beginning of the vowel being the most robust cue. However, the use of these cues varied from speaker to speaker. The * H 1 − * H 2 measurement obtained from male speakers’ production suggested that the contrast being realized may be that of a tense versus lax voice rather than a breathy versus clear voice. It is concluded that the historical breathy and clear phonation distinction in Khmer is preserved among female speakers, but this distinction may be disappearing or have become a tense versus lax distinction among male speakers.

Duration of frication noise required for identification of English fricatives.

Natural speech consonant-vowel (CV) syllables [( f, s, theta, s, v, z, ŏ] followed by [i, u, a]) were computer edited to include 20-70 ms of their frication noise in 10-ms steps as measured from their onset, as well as the entire frication noise. These stimuli, and the entire syllables, were presented to 12 subjects for consonant identification. Results show that the listener does not require the entire fricative-vowel syllable in order to correctly perceive a fricative. The required frication duration depends on the particular fricative, ranging from approximately 30 ms for [s, z] to 50 ms for [f, s, v], while [theta, ŏ] are identified with reasonable accuracy in only the full frication and syllable conditions. Analysis in terms of the linguistic features of voicing, place, and manner of articulation revealed that fricative identification in terms of place of articulation is much more affected by a decrease in frication duration than identification in terms of voicing and manner of articulation.

Measures of the sentence intonation of read and spontaneous speech in American English

The visual abstraction procedure used in previous studies of declination was tested using 12 subjects who each fit the F0 contours of 19 spoken short simple sentences with baselines. These baselines were found to be poorly replicated the fitters. An objective all-points least-squares best-fit procedure was tested on this corpus and on a set of sentences that had been produced in both spontaneous and read speech by six speakers. The all-points linear regression line was a better descriptor of the F0 contours than either baselines or toplines. Declination did not always occur in these simple declarative sentences; there was more variation present in the F0 contours of sentences that had been uttered during spontaneous speech; 35% of the spontaneous sentences did not show declination; 45% of these sentences better fit the breath-group model. Their F0 contours could be described by a level all-points linear regression line followed by a falling terminal segment.