On the impact of downward-directed human voice radiation on ground reflections

Previous studies on vertical or full-spherical directivity patterns of the human voice showed that the human voice has a slightly downward main radiation direction over a wide frequency range. This paper investigates the phoneme-dependencies of human voice radiation in the vertical plane and analyzes to what extent these characteristics affect the ground reflection and the sound incidence at a listener position. The results show that for most phonemes and below 800 Hz, the ground reflection is stronger than the direct sound component because of the downward-directed main radiation. On the contrary, between 800 Hz and 1.6 kHz, the main radiation direction is upward, probably mainly due to diffraction and reflections from the shoulders and the torso.