Frequency Dependencies of the Main Radiation Direction of the Human Voice

For communication in acoustically difficult situations, the directivity of the human voice plays an important role, for example, when we face a person in a meeting or casual conversation. In previous publications, we determined full-spherical directivity patterns of 23 phonemes of different phoneme groups for 13 subjects using a surrounding spherical microphone array. From these data, we determined phoneme-specific directivity patterns and directivity indices. More detailed data analysis revealed specific aspects of human voice directivity, such as a frequency-dependent main radiation direction. In the present study, we analyze the main radiation direction for different phonemes and show that the assumption from previous studies suggesting that the human voice has a slightly downward main radiation direction in a wide frequency range is reasonable. However, the results also reveal significant deviations in the main radiation direction between 800 Hz and 1.6 kHz, probably mainly due to shoulder and torso reflections.