An acoustic and perceptual analysis of /t/ and /d/ flaps in American English

This paper presents an acoustic and perceptual study of alveolar flaps in American English. In the acoustic study, vowel duration differences in disyllabic tokens replicated previous findings in that vowels preceding /d/ were significantly longer than those preceding /t/. Flap frequency was also analyzed based on a method of distinguishing flapped from unflapped stops on a speaker-by-speaker basis. It was discovered that females flapped more often than males and that participants were more likely to flap when they were less aware of the contrast between /t/ and /d/. Contrary to past research, neither word frequency nor morphological complexity affected flap frequency in the present study.In the perceptual study, four naturally produced word pairs were used to manipulate underlying representation (/t/ or /d/), vowel duration preceding the flap, and word frequency. Vowel duration alone did not predict the listeners’ perception of flapped /t/ and /d/; word frequency, where high frequency words were identified correctly more often than low frequency words, and a d-bias, where /d/ flaps were identified correctly more often than /t/ flaps, did prove significant. Unlike previous research, this study uses nonarbitrary values to distinguish flapped from unflapped tokens and draws connections between the acoustic and perceptual results.