Articulatory tradeoffs reduce acoustic variability during American English /r/ production.

The American English phoneme /r/ has long been associated with large amounts of articulatory variability during production. This paper investigates the hypothesis that the articulatory variations used by a speaker to produce /r/ in different contexts exhibit systematic tradeoffs, or articulatory trading relations, that act to maintain a relatively stable acoustic signal despite the large variations in vocal tract shape. Acoustic and articulatory recordings were collected from seven speakers producing /r/ in five phonetic contexts. For every speaker, the different articulator configurations used to produce /r/ in the different phonetic contexts showed systematic tradeoffs, as evidenced by significant correlations between the positions of transducers mounted on the tongue. Analysis of acoustic and articulatory variabilities revealed that these tradeoffs act to reduce acoustic variability, thus allowing relatively large contextual variations in vocal tract shape for /r/ without seriously degrading the primary acoustic cue. Furthermore, some subjects appeared to use completely different articulatory gestures to produce /r/ in different phonetic contexts. When viewed in light of current models of speech movement control, these results appear to favor models that utilize an acoustic or auditory target for each phoneme over models that utilize a vocal tract shape target for each phoneme.     

A modeling investigation of articulatory variability and acoustic stability during American English /r/ production

This paper investigates the functional relationship between articulatory variability and stability of acoustic cues during American English /r/ production. The analysis of articulatory movement data on seven subjects shows that the extent of intrasubject articulatory variability along any given articulatory direction is strongly and inversely related to a measure of acoustic stability (the extent of acoustic variation that displacing the articulators in this direction would produce). The presence and direction of this relationship is consistent with a speech motor control mechanism that uses a third formant frequency (F3) target; i.e., the final articulatory variability is lower for those articulatory directions most relevant to determining the F3 value. In contrast, no consistent relationship across speakers and phonetic contexts was found between hypothesized vocal-tract target variables and articulatory variability. Furthermore, simulations of two speakers' productions using the DIVA model of speech production, in conjunction with a novel speaker-specific vocal-tract model derived from magnetic resonance imaging data, mimic the observed range of articulatory gestures for each subject, while exhibiting the same articulatory/acoustic relations as those observed experimentally. Overall these results provide evidence for a common control scheme that utilizes an acoustic, rather than articulatory, target specification for American English /r/.     

Acoustic modeling of American English /r/

Recent advances in physiological data collection methods have made it possible to test the accuracy of predictions against speaker-specific vocal tracts and acoustic patterns. Vocal tract dimensions for /r/ derived via magnetic-resonance imaging (MRI) for two speakers of American English [Alwan, Narayanan, and Haker, J. Acoust. Soc. Am. 101, 1078-1089 (1997)] were used to construct models of the acoustics of /r/. Because previous models have not sufficiently accounted for the very low F3 characteristic of /r/, the aim was to match formant frequencies predicted by the models to the full range of formant frequency values produced by the speakers in recordings of real words containing /r/. In one set of experiments, area functions derived from MRI data were used to argue that the Perturbation Theory of tube acoustics cannot adequately account for /r/, primarily because predicted locations did not match speakers' actual constriction locations. Different models of the acoustics of /r/ were tested using the Maeda computer simulation program [Maeda, Speech Commun. 1, 199-299 (1982)]; the supralingual vocal-tract dimensions reported in Alwan et al. were found to be adequate at predicting only the highest of attested F3 values. By using (1) a recently developed adaptation of the Maeda model that incorporates the sublingual space as a side branch from the front cavity, and by including (2) the sublingual space as an increment to the dimensions of the front cavity, the mid-to-low values of the speakers' F3 range were matched. Finally, a simple tube model with dimensions derived from MRI data was developed to account for cavity affiliations. This confirmed F3 as a front cavity resonance, and variations in F1, F2, and F4 as arising from mid- and back-cavity geometries. Possible trading relations for F3 lowering based on different acoustic mechanisms for extending the front cavity are also proposed.     

A vocal-tract model of American English /l/

The production of the lateral sounds involves airflow paths around the tongue produced by the laterally inward movement of the tongue toward the midsagittal plane. If contact is made with the palate, a closure is formed in the flow path along the midsagittal line. The effects of the lateral channels on the sound spectrum are not clear. In this study, a vocal-tract model with parallel lateral channels and a supralingual cavity was developed. Analysis shows that the lateral channels with dimensions derived from magnetic resonance images of an American English /l/ are able to produce a pole-zero pair in the frequency range of 2-5 kHz. This pole-zero pair, together with an additional pole-zero pair due to the supralingual cavity, results in a low-amplitude and relatively flat spectral shape in the F3-F5 frequency region of the /l/ sound spectrum.     

A study of sentence stress production in Mandarin speakers of American English

Acoustic characteristics of American English sentence stress produced by native Mandarin speakers are reported. Fundamental frequency (F0), vowel duration, and vowel intensity in the sentence-level stress produced by 40 Mandarin speakers were compared to those of 40 American English speakers. Results obtained from two methods of stress calculation indicated that Mandarin speakers of American English are able to differentiate stressed and unstressed words according to features of F0, duration, and intensity. Although the group of Mandarin speakers were able to signal stress in their sentence productions, the acoustic characteristics of stress were not identical to the American speakers. Mandarin speakers were found to produce stressed words with a significantly higher F0 and shorter duration compared to the American speakers. The groups also differed in production of unstressed words with Mandarin speakers using a higher F0 and greater intensity compared to American speakers. Although the acoustic differences observed may reflect an interference of L1 Mandarin in the production of L2 American English, the outcome of this study suggests no critical divergence between these speakers in the way they implement American English sentence stress.     

Impact factor for gluon production in multi-Regge kinematics in the next-to-leading order

The one-loop correction to the impact factor for gluon production upon the transition of a one-Reggeon state in the t channel to a two-Reggeon state is found. This impact factor is an element of multiparticle amplitudes in multi-Regge kinematics. The correction in question is necessary for developing the theory of Regge and multi-Regge processes. In particular, it is necessary for proving the multi-Regge form of the amplitude in the next-to-leading-logarithm approximation. This correction also makes it possible to complete the verification of the last of the unproven bootstrap conditions for gluon Reggeization and to prove, in this approximation, the validity of the multi-Regge form of the amplitude. All necessary calculations are presented, and an explicit expression for the impact factor in front of all possible color states in the t channel is given.     

Differences in fricative production between children and adults: evidence from an acoustic analysis of /sh/ and /s/

Speech samples of 12 speakers (8 children and 4 adults) producing the fricatives /s/ and/sh/ followed by the vowels /i/ and /u/ were analyzed to locate the major spectral prominences. Results showed that the fricative low-frequency prominences for children's samples differed from those of adults in three important ways: (1) They were generally higher in frequency; (2) they were greater in amplitude relative to higher frequency regions; and (3) they showed greater effects of vowel context. The first finding can be explained by a simple scaling of adult models of fricative production to accommodate children's smaller vocal tracts. The other two findings suggest, however, that there are other anatomical and articulatory differences between children and adults affecting fricative production. The data presented here suggest that one important difference may be the relative sizes of the fricative constriction and the glottal opening.     

Differential use of temporal cues to the /s/-/z/ contrast by native and non-native speakers of English

This study examined the effect of linguistic experience on perception of the English /s/-/z/ contrast in word-final position. The durations of the periodic ("vowel") and aperiodic ("fricative") portions of stimuli, ranging from peas to peace, were varied in a 5 X 5 factorial design. Forced-choice identification judgments were elicited from two groups of native speakers of American English differing in dialect, and from two groups each of native speakers of French, Swedish, and Finnish differing in English-language experience. The results suggested that the non-native subjects used cues established for the perception of phonetic contrasts in their native language to identify fricatives as /s/ or /z/. Lengthening vowel duration increased /z/ judgments in all eight subject groups, although the effect was smaller for native speakers of French than for native speakers of the other languages. Shortening fricative duration, on the other hand, significantly decreased /z/ judgments only by the English and French subjects. It did not influence voicing judgments by the Swedish and Finnish subjects, even those who had lived for a year or more in an English-speaking environment. These findings raise the question of whether adults who learn a foreign language can acquire the ability to integrate multiple acoustic cues to a phonetic contrast which does not exist in their native language.     

Compensating for a bite block in /s/ and /t/ production: palatographic, acoustic, and perceptual data

Electropalatography was used to monitor linguapalatal contact patterns in /s/ and /t/. Talkers often compensated incompletely for a bite block, both immediately after its insertion (sample B1) and after 10 min of practice (sample B2). Significant differences in the number of sensors contacted were noted between normal and bite-block samples for both /s/ and /t/. Differences in length of constriction in /t/, and the A-P location and width of the groove in /s/ were also noted. The two native English subjects compensated better than three Arabic subjects, perhaps because English /s/ and /t/ are formed more posteriorily and with a smaller contact area than their Arabic counterparts. A significant correlation existed between the area and A-P location of linguapalatal contact. All five subjects formed a groove for /s/ in sample B2, but two often did not produce /t/ with complete constriction. This suggests a groove is critical for /s/, but complete constriction is not critical for /t/. The contact patterns in sample B2 more closely resembled normal speech than those in sample B1 in some instances, while in other instances the reverse was true. The conclusion that subjects sometimes overcompensated in sample B2 was supported by the results of detailed acoustic and perceptual analyses for one subject. Taken together, the results suggest that compensation for a bite block is not instantaneous, and that specific parameter values may be encoded in central phonetic representations.     

A qualitative dynamic analysis of reiterant speech production: phase portraits, kinematics, and dynamic modeling

The departure point of the present paper is our effort to characterize and understand the spatiotemporal structure of articulatory patterns in speech. To do so, we removed segmental variation as much as possible while retaining the spoken act's stress and prosodic structure. Subjects produced two sentences from the "rainbow passage" using reiterant speech in which normal syllables were replaced by /ba/ or /ma/. This task was performed at two self-selected rates, conversational and fast. Infrared LEDs were placed on the jaw and lips and monitored using a modified SELSPOT optical tracking system. As expected, when pauses marking major syntactic boundaries were removed, a high degree of rhythmicity within rate was observed, characterized by well-defined periodicities and small coefficients of variation. When articulatory gestures were examined geometrically on the phase plane, the trajectories revealed a scaling relation between a gesture's peak velocity and displacement. Further quantitative analysis of articulator movement as a function of stress and speaking rate was indicative of a language-modulated dynamical system with linear stiffness and equilibrium (or rest) position as key control parameters. Preliminary modeling was consonant with this dynamical perspective which, importantly, does not require that time per se be a controlled variable.     

Perceptual similarity of regional dialects of American English

Previous research on the perception of dialect variation has measured the perceptual similarity of talkers based on regional dialect using only indirect methods. In the present study, a paired comparison similarity ratings task was used to obtain direct measures of perceptual similarity. Naive listeners were asked to make explicit judgments about the similarity of a set of talkers based on regional dialect. The talkers represented four regional varieties of American English and both genders. Results revealed an additive effect of gender and dialect on mean similarity ratings and two primary dimensions of perceptual dialect similarity: geography (northern versus southern varieties) and dialect markedness (many versus few characteristic properties). The present findings are consistent with earlier research on the perception of dialect variation, as well as recent speech perception studies which demonstrate the integral role of talker gender in speech perception.     

Children's recognition of American English consonants in noise

In contrast to the availability of consonant confusion studies with adults, to date, no investigators have compared children's consonant confusion patterns in noise to those of adults in a single study. To examine whether children's error patterns are similar to those of adults, three groups of children (24 each in 4-5, 6-7, and 8-9 yrs. old) and 24 adult native speakers of American English (AE) performed a recognition task for 15 AE consonants in /ɑ/-consonant-/ɑ/ nonsense syllables presented in a background of speech-shaped noise. Three signal-to-noise ratios (SNR: 0, +5, and +10 dB) were used. Although the performance improved as a function of age, the overall consonant recognition accuracy as a function of SNR improved at a similar rate for all groups. Detailed analyses using phonetic features (manner, place, and voicing) revealed that stop consonants were the most problematic for all groups. In addition, for the younger children, front consonants presented in the 0 dB SNR condition were more error prone than others. These results suggested that children's use of phonetic cues do not develop at the same rate for all phonetic features.     

Temporal characteristics of nasalization in children and adult speakers of American English and Korean during production of three vowel contexts

The purpose of this study was to identify and compare the temporal characteristics of nasalization in relation to (1) languages, (2) vowel contexts, and (3) age groups. Two distinct acoustic energies from the mouth and nose were recorded during speech production (/pamap, pimip, pumup/) using two microphones to obtain the absolute and proportional measurements on the acoustic temporal characteristics of nasalization. Twenty-eight normal adults (14 American English and 14 Korean speakers) and 28 normal children (14 American English and 14 Korean speakers) participated in this study. In both languages, adults showed shorter duration of nasalization than children within all three vowel contexts. The high vowel context revealed longer duration of nasalization than the low vowel context in both languages. There was no significant difference of temporal characteristics of nasalization between American English and Korean. Nasalization showed different timing characteristics between children and adults across vowel contexts. The results are discussed in association with developmental coarticulation and the relationship between acoustic consequences of articulatory events and vowel height.     

3s vacancy production in Ar+-Ar and Ar+-He collisions

The 3s vacancy production in Ar⁺-He and Ar⁺-Ar collisions has been studied at impact energies of 100 keV to 550 keV. A comparison is made for the Ar⁺-He system with theoretical calculations based on the quasi-molecular model.     

J/psi production from proton-proton collisions at square root of s=200 GeV

J/psi production has been measured in proton-proton collisions at square root of s=200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at the Relativistic Heavy Ion Collider. Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 4.0+/-0.6(stat)+/-0.6(syst)+/-0.4(abs) mu b. The mean transverse momentum is 1.80+/-0.23(stat)+/-0.16(syst) GeV/c.     

Λ and K s 0 production in pC collisions at 10 GeV/c

The experimental data from the 2-m propane bubble chamber have been analyzed for pC → Λ(K _s ⁰ )X reactions at 10 GeV/c. The estimation of experimental inclusive cross sections for Λ and K _s ⁰ production in the p ¹²C collision is equal to σ_Λ = (13.3 ± 1.7) mb and σ _{K s} ⁰ = (4.6 ± 0.6) mb, respectively. The measured 〈Λ〉/〈π⁺〉 ratio from pC reaction is equal to (5.3 ± 0.8) × 10⁻², and it is approximately two times larger than the 〈Λ〉/〈π⁺〉 ratio simulated by the FRITIOF model and than that of experimental pp reactions at the same energy. The text was submitted by the authors in English.