This study uses multitaper spectral analysis to examine the differences in consonants produced by patients who present with different dentofacial disharmonies (DFD) including severe overbites (Class II), underbites (Class III) and anterior open bites. Previous studies have found that patients with these malocclusion types all produce sibilants and plosives with increased spectral center of gravity and increased spectral spread relative to controls. This result is puzzling since some DFD groups differ from controls in opposite ways. To better understand the articulatory basis of these differences, we apply several spectral shape measures and find that all groups of DFD patients produce /s ʃ t tʃ/ with mid-frequency spectral peaks that are less prominent than those of the control group, but peak frequency measures are largely the same across all groups. This indicates that the DFD patients differ more in sibilant noise source than front cavity size.1.
Keywords: disordered speech; malocclusion; multitaper; sibilant; source-filter.