Lip kinematics for /p/ and /b/ production during whispered and voiced speech

In the absence of voicing, the discrimination of "voiced" and "voiceless" stop consonants in whispered speech relies on such acoustic cues as burst duration and amplitude, and formant transition characteristics. The articulatory processes that generate these features of whispered speech remain speculative. This preliminary investigation examines the articulatory kinematics differences between whispered /p/ and /b/, which may underlie the acoustic differences previously reported for these sounds. Computerized video-tracking methods were used to evaluate kinematic differences between voiced and voiceless stops. Seven subjects produced the target utterances "my papa puppy" and "my baba puppy" in voiced and whispered speech modes. The results revealed that mean peak opening and closing velocities for /b/ were significantly greater than those for /p/ during whispered speech. No differences in peak velocity for either oral closing or opening were observed during voiced speech. The maximum distance between the lips for oral opening for /b/ was significantly greater than for /p/ during whisper, whereas no difference was observed during voiced speech. These data supported the suggestion that whispered speech and voiced speech rely on distinct motor control processes.