Estimation of Transpalatal Nasalance during Production of Voiced Stop Consonants by Noncleft Speakers Using an Oral-Nasal Mask

Abstract

Objective: Our objective was to estimate nasalance due to transpalatal transfer of acoustic energy during production of voiced stop consonants by noncleft speakers. We also determined the relationship between the transpalatal nasalance and fundamental frequency (F0) of the speakers.Method: Participants were 8 men and 10 women (mean age ‫؍‬ 21.9 years, SD ‫؍‬ 4.0) without cleft palate who produced voiced stop (/b d g/) and nasal (/m n /) consonants in syllables embedded in a carrier phrase. Participants also read the Zoo Passage. A divided OroNasal Nasality System mask was used to simultaneously obtain acoustic nasalance and airflow during production of the consonants. Both F0-derived and first formant (F1)-derived nasalance were computed.Results: F0-derived and F1-derived peak nasalance across all speakers ranged from a low of 20% to a high of 80% during production of stop consonants. An estimate of error from the combined sources of transoral transfer of energy (5%) and acoustic crossover between microphones (15%) was no greater than 20%. Analysis of variance revealed no significant effects of the sex of the speakers for either F0-derived or F1-derived nasalance of stops. There was a significant effect of the place of stop production for F0-derived nasalance (p Ͻ .05). Nonsignificant but positive correlations were found between the F0 of the speakers and F0-derived (r ‫؍‬ .25) and F1-derived (r ‫؍‬ .45) nasalance.Conclusions: Transpalatal transfer of oral acoustic energy accounts for most nasalance obtained during production of voiced stop consonants by noncleft speakers. F1-derived nasalance appears to better reflect transpalatal effects. Clinical implications are discussed. KEY WORDS: nasalance, transpalatal nasalance, velopharyngeal closure, voiced stop consonantsNasalance is an acoustic measure that has gained widespread acceptance as a diagnostic correlate of perceived oral-nasal resonance balance (e.g., Dalston et al., 1991;Hardin et al., 1992;Watterson et al., 1996). The term nasalance was coined by Fletcher (1978) to represent the output of a dual-microphone device called TONAR II. Nasalance was defined as the ratio of nasal to oral-plus-nasal acoustic energy in a specific frequency range of speech. This range approximated the energy region of the first formant (F1) of most vowels (350 to

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