(Kenneth N. Stevens)
In the case of some classes of segments, the characteristics of the radiated sound when the articulators are in their target positions are not sufficient to identify all the features of the segment. For example, when there is a complete closure at some point along the length of the vocal tract, as in the case of a stop consonant, no sound emerges from the mouth. Acoustic attributes that identify place of articulation for a stop consonant reside in the time interval when the articulators are moving either toward or away from the constricted configuration. Thus the stop consonant like [d] occurring before a vowel, information about the place of articulation is carried in the 40-odd msec following release of the closure, that is, after the tongue blade has shifted away from the target position for [d] and is moving toward a position appropriate for the following vowel. These acoustic cues reside in a relatively brief, transient time interval. All phonetic segments with the feature [+consonantal] [Chomsky and Halle 1968] seem to have this attribute that at least some acoustic cues for the segment reside in the rapid transition toward or away from the articulatory target and are, in a sense, nonsynchronous with the target.