Which acoustic cue most strongly distinguishes between an unreleased final /p/ and /b/, as in cap versus cab?

• A. Locus frequency of burst
• B. Voice onset time
• C. Vocal fundamental frequency
• D. Duration of the preceding vowel

Answer: (D)

The main idea is that, when the final stop is unreleased, listeners rely on cues from the preceding vowel to tell apart a voiced versus voiceless ending. In English, vowels tend to be longer before a voiced consonant than before a voiceless one. So before the ending that corresponds to a voiced stop, the preceding vowel is longer, while before the ending with a voiceless stop it’s shorter. In cap vs cab, the final stop isn’t released, so the strongest available cue is how long the vowel before it lasts. That’s why the duration of the preceding vowel is the best indicator. The other cues aren’t as informative here because there’s no release burst to measure, and VOT isn’t applicable without a release into a following vowel; F0 differences are less reliable than vowel length in this context.