Auditory perception of distance to rattlesnakes in an audio-visual virtual environment
* Presenting author
Rattlesnakes shake their rattles to drive away animals which they perceive as threatening. Current research has shown that they change the rate at which they rattle according to the distance of an approaching object: the closer the object, the more rattling sounds per second they produce.In an audio-visual VR experiment, we test the hypothesis that this behaviour makes human listeners underestimate their distance to a snake. Humans are passively moved towards an invisible snake in a visual virtual environment (a long-grassed meadow), starting at a distance between 8 m and 1.4 m. Rattling sounds are synthesised and rendered via a vertical loudspeaker array that faithfully transmits loudness and elevation cues. Humans are instructed to stop their movement when they estimate the snake to be exactly 1 m away. We observe that humans stop at significantly larger distances when we simulate a rattling behaviour true to biology, i.e., including the (nonlinear) distance-dependent change in rattling frequency, compared to a virtual snake that rattled at a constant rate. Our data show that the distance-dependent rattling mediates systematically erroneous but useful distance information and is suitable to make human listeners think that they are closer to the snake than they really are.