Cross-Linguistic Nasalance Comparisons: A Review of Speech Sample Sets and Preliminary Consideration of Effect of Lexical Tone.

Introduction: Nasalance is an acoustic representation of perceived nasality with proven clinical and research utility. Its validity is contingent on appropriate speech sample sets and distinct normative databases based on known impact factors such as language and phonetic environment, but little is known about the potential effects of lexical tone on nasalance. Its use in international cross-linguistic studies necessitates definition and added considerations of speech sampling protocol.

Methods: Part I: a methodological review was undertaken using PRISMA (2020), the Scottish Intercollegiate Guidelines Network (SIGN) Methodology Checklist for evaluating the risk of bias, and calculation of effect sizes and/or visual displays using tables showing the grouping of similar data for the synthesis of findings. Part II: a pilot study explored the effect of lexical tone on nasalance in Cantonese, a lexical tone language.

Results: Part I: a total of 17 studies met the inclusion criteria. In addressing possible confounders and minimizing the risk of bias, 13 studies were assigned an overall quality rating of acceptable (+) and the remaining 4, a high rating (++). For the 9-word string, there was a (non-clinical) difference of 3-5% between Swedish and Brazilian-Portuguese, and a moderate effect size for age (d = 0.49); for the consonant-vowel syllables set, clinical differences across languages were identified for adults and between 5 and 10% for children and adolescents. Part II: the pilot study showed a significant effect of lexical tone on nasalance, where nasalance for the high-level tone 1 was significantly higher than that for high-rising tone 2, low-rising tone 5, and low-falling tone 4.

Discussion: There is a need for further evidence from other languages, including tonal languages, to better define the evidence and speech methodology of international cross-linguistic nasalance studies.