Acoustic phenotypes for speech-genetics studies: toward an acoustic marker for residual /s/ distortions

Findings in a prior study series indicate that acoustic markers may have the requisite sensitivity and specificity to discriminate speakers with histories of several types of speech disorders, one of which is posited to be genetically inherited. The present study in this series compares acoustic data from three groups of adolescent speakers. Group 1 speakers had residual dentalized /s/ distortions in conversational speech and histories of significant age-inappropriate deletion and substitution errors. Group 2 speakers also had residual dentalized /s/ distortions in conversational speech, but their speech histories were limited to dentalized distortions of /s/ and other fricatives/affricates. Group 3 speakers had typical speech on assessment and no histories of speech errors. Owing to the limited number of perceptually dentalized /s/ tokens produced by Groups 1 and 2 speakers in a phrase-level speech task, acoustic analyses were completed on /s/ tokens transcribed as correct for speakers in all groups. Moments analyses of /s/ spectra in three words with /s/-initial clusters yielded statistically significant differences and consistent trends for mean spectral frequency and spectral variance for Group 1 compared with Group 2 speakers. These findings for perceptually normal /s/ tokens are interpreted as additional support for the potential of acoustic markers to discriminate speakers' speech-error histories. The discussion considers possible developmental and normalization correlates of the acoustic findings for speakers with each of the two types of speech-error histories studied in this paper.