Individual variability and similarity in horizontal directivity patterns for speech

Human speech directivity patterns are highly complex and temporally dynamic during speech production, with notable variability across individuals. In this paper I will review some of the complexities observed in our horizontal speech directivity production and perception data, including variability and consistencies observed in speech directivity patterns across talkers. Although speech generally becomes more directional towards 0 degrees azimuth as frequency increases, it is clear that the relationship between frequency and directionality is nonmonotonic. Our data indicate this relationship shows some consistency across talkers. For example, peak directionality towards 0 degrees tends to occur around 7-9 kHz, with a slight decrease in directionality at higher frequencies. On the other hand, due to acoustic lobing, minimum directionality towards 0 degrees and corresponding maximum directionality towards 90 degrees tends to occur around 700-800 Hz. Whether these particular phenomena have perceptual consequences for listeners in complex auditory scenes is an intriguing but unresolved question. However, our perceptual data do indicate talker effects on listener detection of talker head orientation, suggesting individual variability in speech directivity patterns may be perceptually relevant.