In American English, initial /bdg/ often lack the acoustic feature taken as the defining feature of voiced stops; intervocalically before unstressed vowel /ptk/ lack aspiration, without which initial stops are not labeled /ptk/. Initially, the two categories differ in the timing of vocal fold adduction and onset of fold vibration, and several acoustic cues, all tied to the VOT difference, have been studied. Medially there is also a difference in the management of the larynx, though it results in a phonetically simpler contrast, one of voicing with no accompanying aspiration difference. Acoustically, however, the list of features that play, or might plausibly play a role is quite large. The word pair rapid‐rabid, for example, might be affected by the following: (1) presence/absence of low‐frequency buzz during the closure interval, (2) duration of closure, (3) F1 offset frequency before closure, (4) F1 offset transition duration, (5) F1 onset frequency following closure, (6) F1 onset transition duration, (7) [æ] duration, (8) F1 “cut‐back” before closure, (9) F1 cutback following closure, (10) VOT cutback before closure, (11) VOT delay after closure, (12) F0 contour before closure, (13) F0 contour after closure, (14) amplitude of [i] relative to [æ], (15) decay time of glottal signal preceding closure, (16) intensity of burst following closure. Even if some of these should turn out to be perceptually negligible, enough of them surely have cue value to make it a formidable task to justify preferring an acoustic to an articulatory account of the distinction between the two English words. [The support of the National Institute of Child Health and Human Development is gratefully acknowledged.]

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