106 Nasalance Scores in Noncleft Individuals: Why Not Zero? CHRISTINA E. GILDERSLEEVE-NEUMANN, M. A. RODGER M. DALSTON,PH.D. Objective: To determine whether oral or nasal acoustic energy is primarily responsible for nonzero nasalance scores observed during the production of nonnasal sentences by individuals with normal speech. Method: Sixty adults with normal speech were asked to read the Zoo pas- sage and produce three sustained vowels, (/i/, /a/ and /u/), with and without nares occlusion. Results: There was a significant decrease in nasalance scores between the unoccluded and occluded conditions for all four stimulus pairs. The mean de- crease across conditions ranged from 8 (/u/) to 25 (/i/). In the unoccluded con- dition, the nasalance score was significantly greater for /i/ than for the other stimuli. Conclusions: The findings suggest that the majority of acoustic energy de- tected by the nasometer’s nasal microphone during the production of nonnasal utterances is the result of sound transmission through the nose. The data ob- tained during this investigation, coupled with information available from other studies, suggest that this may be due to transpalatal transmission. If correct, such a conclusion would have clinical implications for patients with palatal clefts, since residual structural abnormalities and scar tissue in a repaired cleft palate may increase, dampen, or in some way alter transpalatal acoustic trans- mission. Thus, surgical normalization of velopharyngeal port control may not be sufficient to eliminate hypernasality in all patients. KEY WORDS: acoustic transmission, cleft palate, hypernasality, nasalance, na- sometry Over the past 20 years, a great deal of attention has been paid to developing instrumental techniques for assessing ve- lopharyngeal function. The primary purpose of this work has been to provide speech and language pathologists with sup- plemental verification of their clinical impressions. One instru- ment that has achieved considerable popularity among clini- cians is the nasometer. The nasometer is a computer-based instrument that employs microphones on either side of a 25-dB sound separator plate that rests on the upper lip (Fig. 1). The signal from each mi- crophone is filtered and digitized by custom electronic mod- ules. The data are then processed by a computer and accom- panying software. A numeric ratio of nasal acoustic energy to the sum of nasal plus oral acoustic energy is calculated, mul- tiplied by 100 and expressed as a ‘‘nasalance’’ score. There- Ms. Gildersleeve-Neumann is a PhD Candidate, Department of Communi- cation Sciences and Disorders, College of Communication, University of Texas at Austin, Austin, Texas. Dr. Dalston is Amon G. Carter Jr. Professor of Com- munication Sciences and Disorders and Chair, Department of Communication Sciences and Disorders, College of Communication, University of Texas at Austin, Austin, Texas. Submitted October 1999; Accepted February 2000. Reprint requests: Rodger M. Dalston, Ph.D., Department of Communication Sciences and Disorders, University of Texas at Austin, Austin, Texas 78712. E-mail: rdalston@mail.utexas.edu. fore, the output of this instrument provides the user with a score that reflects the relative amount of nasal acoustic energy in a subject’s speech. One of the standard passages routinely used for nasometric assessment of a patient’s speech is known as the Zoo passage. This series of sentences is devoid of nasal consonants. There- fore, a subject with normal velopharyngeal function would be expected to receive a low nasalance score. This assumption has been confirmed repeatedly. Numerous studies report that the Zoo passage nasalance scores of nonnasal speaker groups is somewhere in the range from 10 to 22 (Fletcher et al., 1989; Dalston et al., 1991a, 1991b; Haapanen, 1991; Seaver et al., 1991; Leeper et al., 1992; Litzaw and Dalston, 1992; Dalston et al., 1993; Kavanagh et al., 1994; Watterson et al., 1994; Mahfuzh and Fletcher, 1995; Anderson, 1996; Mayo et al., 1996; Watterson et al., 1996; van Doorn and Purcell, 1998; Nichols, 1999; Scarsellone et al., 1999). Variability among studies appears to depend, in large part, upon speaker dialect, language, or both. Despite nasalance score variability across dialects and lan- guages, subjects with normal oral-nasal resonance balance never manifest nasalance scores that approach zero. The man- ufacturer of this instrument readily acknowledges this fact and suggests that it is due to oral acoustic energy traveling across the sound separator plate and impinging upon the nasal micro- phone: