Fourth formant dip as a correlate of American English flaps

Abstract

Unlike the lower formant frequencies, the fourth formant frequency (F4) is rarely an important acoustic correlate of speech. This study shows evidence of a depression in F4 for some tokens of the American English flap. F4 may be lowered during American English /r/ (Espy‐Wilson et al., 2000) and during retroflex sounds of some languages (e.g., Pima, as found by Avelino and Kim, 2002), but other cues are likely to be more prominent for such sounds. The current project uses a corpus of acoustic measurements of flapped English /t, d/ (e.g., pretty, order) and shows an inconsistent but large drop in F4 at the flap consonant. This occurs predominantly near an /r/, but the F4 drop is timed to the flap, not the /r/. In some tokens, this F4 drop occurs even if the flap is reduced to an approximant, leaving few other acoustic cues to its presence. The F4 drop likely reflects a sublingual cavity resonance caused by an interaction of the tongue positions for /r/ and for a flap. This study presents results on the distribution, frequency of occurrence, and magnitude of the F4 drop. Future research will investigate the perceptual role of the F4 drop.