Closure Duration and the Intervocalic Voiced-Voiceless Distinction in English

Thanks to the means available for speech analysis and synthesis, there is at present considerable knowledge of the acoustic differences whereby we distinguish among the various sounds of English. We know, for example, what the more important acoustic cues are by which listeners decide whether a stop sound is velar, alveolar, or bilabial.1 In the case of the stops, moreover, we know by and large what the acoustic differences are between the members of each of the homorganic pairs p-b, t-d and k-g2 (in other words, between the so-called voiced and voiceless stops3). But we are as yet unable to state with any exactness the extent to which each of these acoustic differences separately affects our ability to discriminate between the two kinds of stops. Moreover, where progress has been made in this direction it is certainly in some measure due to the fact that we have dealt chiefly with the stops in those positions where the voiced-voiceless contrast is phonetically maximal, that is, in initial and final positions. In the first context, aspiration is a prominent feature of the voiceless as against the voiced stops; in the second, the duration of a preceding vowel varies, depending upon whether the stop is of the one kind or the other. For these two positions it is difficult to separate features which contribute to what the phonetician would call voicing as distinct from aspiration and vowel duration, for there is some evidence suggesting that the acoustic correlates of these latter features may suffice as cues to the voicing distinction in the absence of any other differentia.4 There is, however, at least one position in English, namely the post-stressed intervocalic, where the voiced-voiceless distinction is observed even though,