The role of talker sex and body mass index in horizontal speech directivity

Human speech directivity plays a role in speech perception, including speech recognition in complex acoustic environments. Individual variability in speech directivity patterns can arise from differences in the physical attributes of the talker. We examined this variability in horizontal speech directivity using anechoic, multi-channel, high-fidelity recordings of 15 female and 15 male talkers. We calculated the frequency-dependent directivity index (DI) for each talker and tested the effects of frequency, sex, and body mass index (BMI) on the DI. There was a nonmonotonic relationship between DI and frequency. Minimum radiation toward 0º and maximum radiation toward 90° occurred around 700–850 Hz, resulting in a spectral boost at 90° at these frequencies. An effect of sex was limited to frequencies near 1 and 6–7 kHz, with male speech being more directional at these frequencies. BMI was associated with the minimum DI magnitude and the frequency locus of the minimum DI at 0°, with higher BMI associated with a higher frequency locus. Talkers' physical characteristics shape speech directivity, which may have implications for speech perception in real-world, multi-talker acoustic environments. [Work supported by NIH grant R01-DC019745.]