Horizontal directivity patterns differ between vowels extracted from running speech

Directivity patterns for vocalizations radiating from the human mouth have been examined regularly, but phoneme-specific changes in radiation have rarely been identified. This study reports half-plane horizontal directivity up to 20 kHz with 15° angular resolution for /α/, /e/, /i/, /o/, and /u/ extracted from running speech, compared with long-term averaged speech. An effect of vowel category on the directivity index was observed, with /α/ being most directional. Angle-dependent third-octave band weighting functions, useful for simulating real-world listening conditions, highlighted disparities in directivity between running speech and individual vowels. These findings point to rapidly changing dynamic directivity patterns during speech.