Speakers

Nineteen speakers participated in this study (Table 1). There were 11 speakers with Class III (underbite) and 8 speakers with Class I who served as controls. Speakers with Class III ranged in age from 23 to 34 years (mean=21.5); there were 7 males and 4 females. Control speakers ranged in age from 19 to 34 years (mean=24.5); there were 8 females. Controls had no history of speech-language disorders or hearing loss and were judged by an experienced SLP (the 6^th author) to have normal articulation. All speakers were part of a larger study investigating spectral characteristics of DFD patients (Keyser et al., 2022; Lathrop-Marshall et al., 2021). The speakers for the current study were selected to represent distinct ranges of /s/-/ʃ/ spectral distinction as described below. Because of this, no attempt was made to balance sex of the speakers.

Class III Dentofacial Disharmony (DFD) and Class I control speakers’ demographics and spectral characteristics

Notes: M1=first spectral moment, M2=second spectral moment, M3=third spectral moment, M4=fourth spectral moment, NA=not applicable