UC San Diego

Bickley (1982) proposed H1–H2 as an index of the stronger H1 observed for breathy vowels compared to modal ones. Because harmonic amplitudes also vary by overall sound pressure level (SPL), H1 amplitude was normalized to that of H2. Studies have also shown that H1–H2 is well perceived and correlates with glottal open quotient, and thus can be used to infer the articulations leading to changes in perceived quality. Yet in some cases, H1–H2 does not distinguish two voice qualities at statistically significant levels. We claim that this might be due not to the same open quotient between two voice qualities, but to the fact that H1–H2 can be especially noisy to estimate: for example, when f0 is irregular (as in creaky voice qualities), H1–H2 often has large variance that isn’t well modeled statistically. Using several corpora, we show that H1 alone (while controlling for SPL) allows for stronger statistical differentiation of voice categories than H1–H2. We further confirm that H1 can stand in place of H1–H2 as a correlate of glottal constriction. When differentiating voice qualities acoustically, researchers should consider measuring H1 (while controlling for differences in overall SPL) instead of, or in addition to, H1–H2.