Articulatory dynamics of loud and normal speech

A comparison was made between normal and loud productions of bilabial stops and stressed vowels. Simultaneous recordings of lip and jaw movement and the accompanying audio signal were made for four native speakers of Swedish. The stimuli consisted of 12 Swedish vowels appearing in an /i'b_b/ frame and were produced with both normal and increased vocal effort. The displacement, velocity, and relative timing associated with the individual articulators as well as their coarticulatory interactions were studied together with changes in acoustic segmental duration. It is shown that the production of loud as compared with normal speech is characterized by amplification of normal movement patterns that are predictable for the above articulatory parameters. In addition, it was observed that the acoustic durations of bilabial stops were shortened, whereas stressed vowels were lengthened during loud speech production. Two interpretations of the data are offered, viewing loud articulatory behavior as a response to production demands and perceptual constraints, respectively.     

Acoustic properties for place of articulation in nasal consonants

The goal of this study was to determine whether acoustic properties could be derived for English labial and alveolar nasal consonants that remain stable across vowel contexts, speakers, and syllable positions. In experiment I, critical band analyses were conducted of five tokens each of [m] and [n] followed by the vowels [i e a o u] spoken by three speakers. Comparison of the nature of the changes in the spectral patterns from the murmur to the release showed that, for labials, there was a greater change in energy in the region of Bark 5-7 relative to that of Bark 11-14, whereas, for alveolars, there was a greater change in energy from the murmur to the release in the region of Bark 11-14 relative to that of Bark 5-7. Quantitative analyses of each token indicated that over 89% of the utterances could be appropriately classified for place of articulation by comparing the proportion of energy change in these spectral regions. In experiment II, the spectral patterns of labial and alveolar nasals produced in the context of [s] + nasal ([ m n]) + vowel ([ i e a o u]) by two speakers were explored. The same analysis procedures were used as in experiment I. Eighty-four percent of the utterances were appropriately classified, although labial consonants were less consistently classified than in experiment I. The properties associated with nasal place of articulation found in this study are discussed in relation to those associated with place of articulation in stop consonants and are considered from the viewpoint of a more general theory of acoustic invariance.     

Acoustic cues discriminating german obstruents in place and manner of articulation

This study focuses on the extraction of robust acoustic cues of labial and alveolar voiceless obstruents in German and their acoustic differences in the speech signal to distinguish them in place and manner of articulation. The investigated obstruents include the affricates [pf] and [ts], the fricatives [f] and [s] and the stops [p] and [t]. The target sounds were analyzed in word-initial and word-medial positions. The speech data for the analysis were recorded in a natural environment, deliberately containing background noise to extract robust cues only. Three methods of acoustic analysis were chosen: (1) temporal measurements to distinguish the respective obstruents in manner of articulation, (2) static spectral characteristics in terms of logarithmic distance measure to distinguish place of articulation, and (3) amplitudinal analysis of discrete frequency bands as a dynamic approach to place distinction. The results reveal that the duration of the target phonemes distinguishes these in manner of articulation. Logarithmic distance measure, as well as relative amplitude analysis of discrete frequency bands, identifies place of articulation. The present results contribute to the question, which properties are robust with respect to variation in the speech signal.     

A study of jaw coarticulatory resistance and aggressiveness for Catalan consonants and vowels

The goal of this study is to investigate coarticulatory resistance and aggressiveness for the jaw in Catalan consonants and vowels and, more specifically, for the alveolopalatal nasal //[symbol see text]/ and for dark /l/ for which there is little or no data on jaw position and coarticulation. Jaw movement data for symmetrical vowel-consonant-vowel sequences with the consonants /p, n, l, s, ∫, [ symbol see text], k/ and the vowels /i, a, u/ were recorded by three Catalan speakers with a midsagittal magnetometer. Data reveal that jaw height is greater for /s, ∫/ than for /p, [see text]/, which is greater than for /n, l, k/ during the consonant, and for /i, u/ than for /a/ during the vowel. Differences in coarticulatory variability among consonants and vowels are inversely related to differences in jaw height, i.e., fricatives and high vowels are most resistant, and /n, l, k/ and the low vowel are least resistant. Moreover, coarticulation resistant phonetic segments exert more prominent effects and, thus, are more aggressive than segments specified for a lower degree of coarticulatory resistance. Data are discussed in the light of the degree of articulatory constraint model of coarticulation.     

Laryngeal function and vocal fatigue after prolonged reading in individuals with unilateral vocal fold paralysis

The purpose of the present study was to examine the effect of prolonged loud reading, intended to induce fatigue, on vocal function in adults with unilateral vocal fold paralysis (UVFP). Subjects were 20 adults, 37–60 years old, with UVFP secondary to recurrent laryngeal nerve paralysis. Subjective ratings and instrumental measures of vocal function were obtained before and after reading. Statistical analysis revealed subjects rated their vocal quality and physical effort for voicing more severely following prolonged loud reading, whereas expert raters did not detect a significant perceptual difference in vocal quality. Reading fundamental frequency (Fo) was significantly increased following prolonged loud reading, as were mean airflow rates at all pitch conditions. Maximum phonation times for comfort and low pitches significantly decreased during posttests. Multiple regression analyses revealed significant associations between ratings of posttest physical effort and select posttest measures. Interpretation of results indicates the prolonged loud reading task was successful in vocally fatiguing most of the UVFP subjects. Key physiologic correlates of vocal fatigue, in individuals with UVFP, include further reduction of glottic efficiency, resulting in decreased regulation of glottic airflow and a temporary destabilization of speaking fundamental frequency.     

Acoustic effects of variation in vocal effort by men, women, and children

The acoustic effects of the adjustment in vocal effort that is required when the distance between speaker and addressee is varied over a large range (0.3-187.5 m) were investigated in phonated and, at shorter distances, also in whispered speech. Several characteristics were studied in the same sentence produced by men, women, and 7-year-old boys and girls: duration of vowels and consonants, pausing and occurrence of creaky voice, mean and range of F0, certain formant frequencies (F1 in [a] and F3), sound-pressure level (SPL) of voiced segments and [s], and spectral emphasis. In addition to levels and emphasis, vowel duration, F0, and F1 were substantially affected. "Vocal effort" was defined as the communication distance estimated by a group of listeners for each utterance. Most of the observed effects correlated better with this measure than with the actual distance, since some additional factors affected the speakers' choice. Differences between speaker groups emerged in segment durations, pausing behavior, and in the extent to which the SPL of [s] was affected. The whispered versions are compared with the phonated versions produced by the same speakers at the same distance. Several effects of whispering are found to be similar to those of increasing vocal effort.     

What's so special about singers?

Research on singers' breathing, phonation and articulation patterns during singing is reviewed and comparisons are made with typical speech patterns. It is found that singers' and nonsingers' use of the voice differ in several respects. The reasons for these differences are discussed and explanations are proposed referring to the special demands raised on singers with respect to economization of vocal effort and flexibility of phonation.     

Coarticulatory influences on the perceived height of nasal vowels

Certain of the complex spectral effects of vowel nasalization bear a resemblance to the effects of modifying the tongue or jaw position with which the vowel is produced. Perceptual evidence suggests that listener misperceptions of nasal vowel height arise as a result of this resemblance. Whereas previous studies examined isolated nasal vowels, this research focused on the role of phonetic context in shaping listeners' judgments of nasal vowel height. Identification data obtained from native American English speakers indicated that nasal coupling does not necessarily lead to listener misperceptions of vowel quality when the vowel's nasality is coarticulatory in nature. The perceived height of contextually nasalized vowels (in a [bVnd] environment) did not differ from that of oral vowels (in a [bVd] environment) produced with the same tongue-jaw configuration. In contrast, corresponding noncontextually nasalized vowels (in a [bVd] environment) were perceived as lower in quality than vowels in the other two conditions. Presumably the listeners' lack of experience with distinctive vowel nasalization prompted them to resolve the spectral effects of noncontextual nasalization in terms of tongue or jaw height, rather than velic height. The implications of these findings with respect to sound changes affecting nasal vowel height are also discussed.     

The control of air flow during loud soprano singing

Previous research on the special characteristics of the professional singing voice has at least partially explained how singers can commonly use much higher lung pressures than nonsingers without vocal damage or excessive air flow during the voiced sounds. In this study, the control of air flow during the unvoiced consonants is examined for an operatic-style soprano. It was found that this singer could maintain a low average air flow during the consonants even though the lung pressure reached values over five times those used during normal conversational speech. The air flow was kept low primarily by the use of a number of mechanisms involving rapid, accurate, coordinated valving of the air flow at the point of articulation and at the glottis.     

Consonant confusions in white noise

The classic [MN55] confusion matrix experiment (16 consonants, white noise masker) was repeated by using computerized procedures, similar to those of Phatak and Allen (2007). ["Consonant and vowel confusions in speech-weighted noise," J. Acoust. Soc. Am. 121, 2312-2316]. The consonant scores in white noise can be categorized in three sets: low-error set [/m/, /n/], average-error set [/p/, /t/, /k/, /s/, /[please see text]/, /d/, /g/, /z/, /Z/], and high-error set /f/theta/b/, /v/, /E/,/theta/]. The consonant confusions match those from MN55, except for the highly asymmetric voicing confusions of fricatives, biased in favor of voiced consonants. Masking noise cannot only reduce the recognition of a consonant, but also perceptually morph it into another consonant. There is a significant and systematic variability in the scores and confusion patterns of different utterances of the same consonant, which can be characterized as (a) confusion heterogeneity, where the competitors in the confusion groups of a consonant vary, and (b) threshold variability, where confusion threshold [i.e., signal-to-noise ratio (SNR) and score at which the confusion group is formed] varies. The average consonant error and errors for most of the individual consonants and consonant sets can be approximated as exponential functions of the articulation index (AI). An AI that is based on the peak-to-rms ratios of speech can explain the SNR differences across experiments.     

Effects of a vocally fatiguing task and systemic hydration on phonation threshold pressure

Phonation threshold pressure (PTP), effort for speaking, and vibratory closure pattern were assessed in 4 women with normal untrained voices after 2 hours of loud reading. PTP generally increased after this vocally fatiguing task at conversational pitch and 10%, 50%, and especially 80% of the pitch range. Increased systemic hydration by drinking water appeared to attenuate and/or delay the elevation of PTP for 3 subjects, at least at the highest pitch tested. Effort for speaking increased consistently throughout the loud reading task and subsequently decreased after 15 minutes of vocal silence. Upon videostroboscopic examination of the larynx, 3 subjects demonstrated spindle-shaped vibratory closure patterns on occasion after loud reading. The results provide preliminary support for increasing water consumption to reduce or delay some vocal-function changes after prolonged loud phonation in untrained speakers.     

Positional targets for lingual consonants defined using electromagnetic articulography

The study examined the positional targets for lingual consonants defined using a point-parameterized approach with Wave (NDI, Waterloo, ON, Canada). The overall goal was to determine which consonants had unique tongue positions with respect to other consonants. Nineteen talkers repeated vowel-consonant-vowel (VCV) syllables that included consonants /t, d, s, z, , k, g/ in symmetrical vowel contexts /i, u, a/, embedded in a carrier phrase. Target regions for each consonant, characterized in terms of x,y,z tongue positions at the point of maximum tongue elevation, were extracted. Distances and overlaps were computed between all consonant pairs and compared to the distances and overlaps of their contextual targets. Cognates and postalveolar homorganics were found to share the location of their target regions. On average, alveolar stops showed distinctively different target regions than alveolar fricatives, which in turn showed different target region locations than the postalveolar consonants. Across talker variability in target locations was partially explained by differences in habitual speaking rate and hard palate characteristics.     

Lip kinematics in long and short stop and fricative consonants

This paper examines lip and jaw kinematics in the production of labial stop and fricative consonants where the duration of the oral closure/constriction is varied for linguistic purposes. The subjects were speakers of Japanese and Swedish, two languages that have a contrast between short and long consonants. Lip and jaw movements were recorded using a magnetometer system. Based on earlier work showing that the lips are moving at a high velocity at the oral closure, it was hypothesized that speakers could control closure/constriction duration by varying the position of a virtual target for the lips. According to this hypothesis, the peak vertical position of the lower lip during the oral closure/constriction should be higher for the long than for the short consonants. This would result in the lips staying in contact for a longer period. The results show that this is the case for the Japanese subjects and one Swedish subject who produced non-overlapping distributions of closure/ constriction duration for the two categories. However, the peak velocity of the lower lip raising movement did not differ between the two categories. Thus if the lip movements in speech are controlled by specifying a virtual target, that control must involve variations in both the position and the timing of the target.     

Information transfer analysis: a first look at estimation bias

Information transfer analysis [G. A. Miller and P. E. Nicely, J. Acoust. Soc. Am. 27, 338-352 (1955)] is a tool used to measure the extent to which speech features are transmitted to a listener, e.g., duration or formant frequencies for vowels; voicing, place and manner of articulation for consonants. An information transfer of 100% occurs when no confusions arise between phonemes belonging to different feature categories, e.g., between voiced and voiceless consonants. Conversely, an information transfer of 0% occurs when performance is purely random. As asserted by Miller and Nicely, the maximum-likelihood estimate for information transfer is biased to overestimate its true value when the number of stimulus presentations is small. This small-sample bias is examined here for three cases: a model of random performance with pseudorandom data, a data set drawn from Miller and Nicely, and reported data from three studies of speech perception by hearing impaired listeners. The amount of overestimation can be substantial, depending on the number of samples, the size of the confusion matrix analyzed, as well as the manner in which data are partitioned therein.     

Method for the location of burst-onset spectra in the auditory-perceptual space: a study of place of articulation in voiceless stop consonants

A method for distinguishing burst onsets of voiceless stop consonants in terms of place of articulation is described. Four speakers produced the voiceless stops in word-initial position in six vowel contexts. A metric was devised to extract the characteristic burst-friction components at burst onset. The burst-friction components, derived from the metric as sensory formants, were then transformed into log frequency ratios and plotted as points in an auditory-perceptual space (APS). In the APS, each place of articulation was seen to be associated with a distinct region, or target zone. The metric was then applied to a test set of words with voiceless stops preceding ten different vowel contexts as produced by eight new speakers. The present method of analyzing voiceless stops in English enabled us to distinguish place of articulation in these new stimuli with 70% accuracy.     

Contextual effects on lingual-mandibular coordination

Coordination between intrinsic and jaw-related components of tongue blade movement during the articulation of the alveolar consonant /t/ was examined across changes in phonetic context. Tongue-jaw interactions included compensatory responses of one articulatory component to a contextual effect on the position of the other articulatory component. A similar reciprocity has been observed in studies that introduced artificial perturbation of jaw position and studies of patterns of token-to-token variability. Thus the lingual-mandibular complex seems to respond in a similar manner to at least some natural and artificial perturbations.     

Perceptual integration of the murmur and formant transitions for place of articulation in nasal consonants

This study reassessed the role of the nasal murmur and formant transitions as perceptual cues for place of articulation in nasal consonants across a number of vowel environments. Five types of computer-edited stimuli were generated from natural utterances consisting of [m n] followed by [i e a o u]: (1) full murmurs; (2) transitions plus vowel segments; (3) the last six pulses of the murmur; (4) the six pulses starting from the beginning of the formant transitions; and (5) the six pulses surrounding the nasal release (three pulses before and three pulses after). Results showed that the murmur provided as much information for the perception of place of articulation as did the transitions. Moreover, the highest performance scores for place of articulation were obtained in the six-pulse condition containing both murmur and transition information. The data support the view that it is the combination of nasal murmur plus formant transitions which forms an integrated property for the perception of place of articulation.     

Acoustic parameters measured by a formant-estimating speech processor for a multiple-channel cochlear implant

In order to assess the limitations imposed on a cochlear implant system by a wearable speech processor, the parameters extracted from a set of 11 vowels and 24 consonants were examined. An estimate of the fundamental frequency EF 0 was derived from the zero crossings of the low-pass filtered envelope of the waveform. Estimates of the first and second formant frequencies EF 1 and EF 2 were derived from the zero crossings of the waveform, which was filtered in the ranges 300-1000 and 800-4000 Hz. Estimates of the formant amplitudes EA 1 and EA 2 were derived by peak detectors operating on the outputs of the same filters. For vowels, these parameters corresponded well to the first and second formants and gave sufficient information to identify each vowel. For consonants, the relative levels and onset times of EA 1 and EA 2 and the EF 0 values gave cues to voicing. The variation in time of EA 1, EA 2, EF 1, and EF 2 gave cues to the manner of articulation. Cues to the place of articulation were given by EF 1 and EF 2. When pink noise was added, the parameters were gradually degraded as the signal-to-noise ratio decreased. Consonants were affected more than vowels, and EF 2 was affected more than EF 1. Results for three good patients using a speech processor that coded EF 0 as an electric pulse rate, EF 1 and EF 2 as electrode positions, and EA 1 and EA 2 as electric current levels confirmed that the parameters were useful for recognition of vowels and consonants. Average scores were 76% for recognition of 11 vowels and 71% for 12 consonants in the hearing-alone condition. The error rates were 4% for voicing, 12% for manner, and 25% for place.     

Stop consonant place perception with single-formant stimuli: evidence for the role of the front-cavity resonance.

The third formant and the second formant were found on average to cue the place of articulation of intervocalic stop consonants equally well when the stop consonants occurred before the vowel/i/. This result and others provide some support for the notion that the fundamental resonance of the front cavity plays an important role in the perception of the phonetic dimension of place of articulation.     

Comparing tongue shapes from ultrasound imaging using smoothing spline analysis of variance

Ultrasound imaging of the tongue is increasingly common in speech production research. However, there has been little standardization regarding the quantification and statistical analysis of ultrasound data. In linguistic studies, researchers may want to determine whether the tongue shape for an articulation under two different conditions (e.g., consonants in word-final versus word-medial position) is the same or different. This paper demonstrates how the smoothing spline ANOVA (SS ANOVA) can be applied to the comparison of tongue curves [Gu, Smoothing Spline ANOVA Models (Springer, New York, 2002)]. The SS ANOVA is a technique for determining whether or not there are significant differences between the smoothing splines that are the best fits for two data sets being compared. If the interaction term of the SS ANOVA model is statistically significant, then the groups have different shapes. Since the interaction may be significant even if only a small section of the curves are different (i.e., the tongue root is the same, but the tip of one group is raised), Bayesian confidence intervals are used to determine which sections of the curves are statistically different. SS ANOVAs are illustrated with some data comparing obstruents produced in word-final and word-medial coda position.