Vowel height and the perception of consonant nasality

The relation of velopharyngeal coupling area and vocal tract scaling to identification of stop-nasal cognates

The purpose of this study was to determine whether the threshold of velopharyngeal (VP) coupling area at which listeners switch from identifying a consonant as a stop to a nasal in North American English was different for speech produced by a model based on an adult male, an adult female, and a 4-year-old child. V1CV2 stimuli were generated with a speech production model that encodes phonetic segments as relative acoustic targets imposed on an underlying vocal tract and laryngeal structure that can be scaled according to sex and age. Each V1CV2 was synthesized with a set of VP coupling functions whose maximum area ranged from 0 to 0.1 cm2. Results showed that scaling the vocal tract and vocal folds had essentially no effect on the VP coupling area at which listener identification shifted from stop to nasal. The range of coupling areas at which the crossover occurred was 0.037-0.049 cm2 for the male model, 0.040-0.055 cm2 for the female model, and 0.039-0.052 cm2 for the 4-year-old child model, and overall mean was 0.044 cm2. Calculations of band limited peak nasalance indicated that 85% peak nasalance during the consonant was well aligned with listener responses.

Vowel height and velum position in German: Insights from a real-time magnetic resonance imaging study

Velum position was analysed as a function of vowel height in German tense and lax vowels preceding a nasal or oral consonant. Findings from previous research suggest an interdependence between vowel height and the degree of velum lowering, with a higher velum during high vowels and a more lowered velum during low vowels. In the current study, data were presented from 33 native speakers of Standard German who were measured via non-invasive high quality real-time magnetic resonance imaging. The focus was on exploring the spatiotemporal extent of velum lowering in tense and lax /a, i, o, ø/, which was done by analysing velum movement trajectories over the course of VN and VC sequences in CVNV and CVCV sequences by means of functional principal component analysis. Analyses focused on the impact of the vowel category and vowel tenseness. Data indicated that not only the position of the velum was affected by these factors but also the timing of velum closure. Moreover, it is argued that the effect of vowel height was to be better interpreted in terms of the physiological constriction location of vowels, i.e., the specific tongue position rather than phonetic vowel height.

The relation of velopharyngeal coupling area to the identification of stop versus nasal consonants in North American English based on speech generated by acoustically driven vocal tract modulations

The purpose of this study was to determine the threshold of velopharyngeal coupling area at which listeners switch from identifying a consonant as a stop to a nasal in North American English, based on V₁CV₂ stimuli generated with a speech production model that encodes phonetic segments as relative acoustic targets. Each V₁CV₂ was synthesized with a set of velopharyngeal coupling functions whose area ranged from 0 to 0.1 cm². Results show that consonants were identified by listeners as a stop when the coupling area was less than 0.035-0.057 cm², depending on place of articulation and final vowel. The smallest coupling area (0.035 cm²) at which the stop-to-nasal switch occurred was found for an alveolar consonant in the /ɑCi/ context, whereas the largest (0.057 cm²) was for a bilabial in /ɑCɑ/. For each stimulus, the balance of oral versus nasal acoustic energy was characterized by the peak nasalance during the consonant. Stimuli with peak nasalance below 40% were mostly identified by listeners as stops, whereas those above 40% were identified as nasals. This study was intended to be a precursor to further investigations using the same model but scaled to represent the developing speech production system of male and female talkers.

Differences in nasalance and nasality perception between Texas South and Midland dialects

While previous research has primarily concerned the dialectal influence on speakers' production of oral-nasal balance, quantitatively represented by nasalance, information on cross-dialectal variation in nasality perception is limited. This study investigated the effects of speakers'/listeners' dialectal background on oral-nasal balance characteristics estimated by nasalance, as well as nasality perception measured by direct magnitude estimation with modulus. Represented by two geographically distinct regions, Texas South and Midland dialects were of special interest given that the two dialects lie at opposite ends of normal nasalance variation [Awan, Bressmann, Poburka, Roy, Sharp, and Watts. (2015). J. Speech Lang. Hear. Res. 58, 69-77]. Mean nasalance of various speech stimuli and direct magnitude estimation ratings on synthesized vowel stimuli with varying degrees of simulated nasalization were obtained from 62 participants (31 Texas South, 31 Midland). The results revealed that the two dialectal groups significantly differed in nasalance scores and nasality ratings, with Texas South exhibiting higher nasalance for standardized passage readings and assigning higher nasality ratings on the synthetic auditory stimuli than Midland. These findings indicate that, in addition to production variations of oral-nasal balance characteristics, perceptual variations of nasality exist at a dialectal level.

Validity of the Nasometer Measuring the Temporal Characteristics of Nasalization

Objective:

To examine the validity of the Nasometer (KayPENTAX, Lincoln Park, NJ) in measuring the temporal characteristics of nasalization by comparing the Nasometer measures to the measures from an external criterion procedure.

Design:

Speech samples consisted of three rate-controlled nonsense syllables, which varied in their vowel compositions: /izinizi/, /azanaza/, and /uzunuzu/. Acoustic data were recorded simultaneously through the Nasometer and an external criterion procedure (a specialized microphone set that collected acoustic signals separately for the nasal and oral channels). Speech segment durations measured from the two instrumental conditions were compared on the Nasometer display and the Computerized Speech Lab (KayPENTAX, Lincoln Park, NJ) display. Five durational variables were measured: total utterance duration, nasal onset interval, nasal consonant duration, nasal offset interval, and total nasalization duration.

Participants:

Fourteen normal adults who speak American English as their first language participated in the study.

Results:

No significant differences were found between the measures from the Nasometer and those from an external criterion procedure in all the durational variables pertinent to nasalization. Different vowels, however, yielded significantly different patterns in these durational variables, in which the low vowel /a/ context revealed significantly longer total nasalization duration than did the high vowel /i/ and /u/ contexts.

Conclusions:

The results suggest that the Nasometer can be used as a valid tool to measure the temporal characteristics underlying nasalization and confirm significant vowel effects on the temporal patterns of nasalization.

An acoustic study of nasal consonants in three Central Australian languages

This study presents nasal consonant data from 21 speakers of three Central Australian languages: Arrernte, Pitjantjatjara and Warlpiri. The six nasals considered are bilabial /m/, dental /n/, alveolar /n/, retroflex /ɳ/, alveo-palatal /ɲ/, and velar /ŋ/. Nasal formant and bandwidth values are examined, as are the locations of spectral minima. Several differences are found between the bilabial /m/ and the velar /ŋ/, and also the palatal /ɲ/. The remaining coronal nasals /n n ɳ/ are not well differentiated within the nasal murmur, but their average bandwidths are lower than for the other nasal consonants. Broader spectral shape measures (Centre of Gravity and Standard Deviation) are also considered, and comparisons are made with data for stops and laterals in these languages based on the same spectral measures. It is suggested that nasals are not as easily differentiated using the various measures examined here as are stops and laterals. It is also suggested that existing models of nasal consonants do not fully account for the observed differences between the various nasal places of articulation; and that oral formants, in addition to anti-formants, contribute substantially to the output spectrum of nasal consonants.

Comparison of nasal acceleration and nasalance across vowels

PURPOSE

The purpose of this study was to determine the performance of normalized nasal acceleration (NNA) relative to nasalance as estimates of nasalized versus nonnasalized vowel and sentence productions.

METHOD

Participants were 18 healthy speakers of American English. NNA was measured using a custom sensor, and nasalance was measured using the KayPentax Nasometer II. Speech stimuli consisted of CVC syllables with the vowels (//, /æ/, /i/, /u/) and sentences loaded with high front, high back, low front, and low back vowels in both nasal and nonnasal contexts.

RESULTS

NNA showed a small but significant effect of the vowel produced during syllable stimuli but no significant effect of vowel loading during sentence stimuli. Nasalance was significantly affected by the vowel being produced during both syllables and sentences with large effect sizes. Both NNA and nasalance were highly sensitive and specific to nasalization.

CONCLUSIONS

NNA was less affected by vowel than nasalance. Discrimination of nasal versus nonnasal stimuli using NNA and nasalance was comparable, suggesting potential for use of NNA for biofeedback applications. Future work to improve calibration of NNA is needed to lower intersubject variability.

A comparison of equal-appearing interval scaling and direct magnitude estimation of nasal voice quality

Listeners rated the nasality of synthesized vowels using two psychophysical scaling methods (equal-appearing interval scaling and direct magnitude estimation). A curvilinear relationship between equal-appearing interval ratings and direct magnitude estimations of nasality indicated that nasality is a prothetic rather than metathetic dimension. It also was shown that the use of direct magnitude estimation results in nasality ratings that are more consistent and reliable. The results of this experiment are discussed in relation to other studies that have examined the validity and reliability of equal-appearing interval scaling of voice quality. Additionally, there is a discussion of methodological issues for future research and the implications of the findings for clinical and research purposes.

Role of the soft palate in laryngeal functions and selected voice qualities. Simultaneous velolaryngeal videoendoscopy

The role of the soft palate in normal laryngeal functions and in the production of selected voice qualities was studied by a simultaneous velolaryngeal videoendoscopy technique. For this technique, the Olympus ENF-P flexible nasopharyngolaryngoscope was passed via one nostril to study the function of the larynx, while the Hopkins 70 degrees rhinoscopic telescope was passed via the other nostril to study the function of the soft palate and velopharyngeal closure. A Kay Elemetrics DSP Sona-Graph, model 5500, was used to analyze a complex vocal figure of five consecutive voice qualities, three of which were nasal, and two, oral. Simultaneous velolaryngeal videoendoscopy proved to be of great value for the understanding of the interaction of velar and laryngeal functions and for clarifying the mechanisms of nasal and twang qualities.