Nasalization Amplitude-Timing Characteristics of Speakers With and Without Cleft Palate

The Role of Instructions in Motor Learning of Oral Versus Nasalized Speech Targets

PURPOSE

The purpose of this study was to investigate how general, implicit instructions with auditory-perceptual emphasis; specific, explicit instructions with biomechanical focus; or both affect learning of oral-nasal balance control in speech.

METHOD

Thirty healthy, vocally untrained participants were assigned to one of three instructional groups (i.e., implicit, explicit, and integrated) and learned to produce oral versus nasalized vowel-, syllable-, and phrase-level targets during once-weekly sessions over 4 weeks. Learning gains and performance variability were analyzed using nasometry.

RESULTS

We observed a significant main effect of instruction type on learning gains at phrase level (p = .016). Specifically, the integrated group (M = 59.8%) significantly outperformed the explicit group (M = 37.9%) and numerically outperformed the implicit group (M = 45.1%). For nasalized phrase targets, results revealed a significant main effect of instruction type on performance variability (p = .042), but pairwise comparisons between instruction groups were not significant.

CONCLUSIONS

The integration of implicit processes via auditory-perceptual modeling and explicit processes via relevant biomechanical directives resulted in larger motor learning gains, especially at higher levels of task complexity (i.e., phrase) compared to providing implicit or explicit instruction alone. The higher performance variability (i.e., less stable productions) that was sometimes induced by explicit instruction did not negatively impact learning when integrated with implicit instruction. Clinical implications for speech/voice therapy models are discussed.

Comparing the Temporal Aspects of Velopharyngeal Closure in Children with and without Cleft Palate

INTRODUCTION

Children with cleft palate exhibit differences in the 4 temporal components of nasalization (nasal onset and offset intervals, nasal consonant duration, and total speech duration), with various patterns having been noted based on different languages. Thus, the current study aimed to examine the temporal aspects of velopharyngeal closure in children with and without cleft palate; this is the first study to do so in the Turkish language.

METHODS

This study evaluated and compared the 4 temporal characteristics of velopharyngeal closure in children (aged 6-10 years) with (n = 28) and without (n = 28) cleft palate using nonword consonant and vowel speech samples, including the bilabial nasal-to-stop combination /mp/ and the velar nasal-to-stop combination /ηk/. Acoustic data were recorded using a nasometer, after which acoustic waveforms were examined to determine the 4 temporal components of nasalization. Flexible nasoendoscopy was then used to evaluate velopharyngeal closure patterns.

RESULTS

With regard to the 4 closure patterns, significant differences in the nasal offset interval (F4-25 = 10.213, p = 0.04; p < 0.05) and the nasal consonant duration ratio (F4-25 = 12.987, p = 0.02; p < 0.05) were observed for only /ampa/. The coronal closure pattern showed the longest closure duration (0.74 s). Children with cleft palate showed prolonged temporal parameters in all 4 characteristics, reflecting oral-nasal resonance imbalances. In particular, the low vowel sound /a/ was significantly more prolonged than the high vowel sounds /i/ and /u/.

CONCLUSIONS

The examined temporal parameters offer more accurate characterizations of velopharygeal closure, thereby allowing more accurate clinical assessments and more appropriate treatment procedures. Children with cleft palate showed longer nasalization durations compared to those without the same. Thus, the degree of hypernasality in children with cleft palate may affect the temporal aspects of nasalization.

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.

Effects of regional dialect on oral-nasal balance and nasality perception

While cross-dialectal variations in nasalance have been investigated in previous studies, the influence of regional dialect on listeners' perceptual ratings of nasality has received limited research attention. This study explored cross-dialectal differences in the production of oral-nasal balance and the perception of nasality, with special emphasis on Inland North (IN) and Midland (M) dialects in the USA. Twenty-six adults representing the IN (n = 15) and M (n = 11) dialects participated in the study. Oral-nasal balance characteristics and nasality perception were compared between dialects using mean nasalance of various speech stimuli, measured via nasometry, and perceptual ratings of nasality of synthetic vowel stimuli, measured using direct magnitude estimation (DME). Despite similar mean nasalance scores between two regional dialects for standardized passage readings and sustained vowels, IN and M groups significantly differed in their perceptual ratings of nasality, with the DMEs of IN listeners being consistently and significantly higher, i.e. more nasal, than those of M listeners. Our findings provide evidence for perceptual variations of nasality that may exist at a dialectal level in addition to cross-linguistic variations in the perception of nasality as reported by Lee et al. (2008). Further research is needed to determine to what extent perceptual variations of nasality exist in other dialects and how these variations manifest in perceptual judgments of hypernasality and its severity ratings.