Voiced and voiceless stops in initial position are known to differ in Voice Onset Time; they may also differ in closure duration and the duration of closure voicing. Besides the voicing distinction, such factors as the position of the stop in a word or utterance, the stop's place of articulation, and the stress of adjacent syllables will also affect these measures. Data from the literature have been extended with new acoustic measurements for English, Swedish, and other languages. While there is some variation across languages, general patterns, which might be attributable to vocal tract physiology, can be identified. In an attempt to account for these patterns, an electrical analog of vocal tract aerodynamics can be used to study the probable effects of place of articulation and syllable stress on closure voicing offset. The model allows variation of subglottal pressure, glottal area, supralaryngeal cavity volume, wall mechanics, and oral constriction geometry. The extent to which these variables determine universal, presumably inherent, patterns of variation will be considered.