Perception of the size and speed of rolling balls by sound

In everyday life, we listen to the properties of sources that generate sound, not to properties of the sound itself. But what properties of the sound source can we identify and what is it in the sound that informs us about these properties? This paper reports three experiments investigating the auditory perception of the size and the speed of wooden balls rolling over a wooden plate on the basis of recorded sounds. Experiment I showed that listeners are able to choose the larger ball from paired sounds. Experiment II showed that listeners are able to discriminate between the sounds of balls rolling with different speeds. However, some listeners reversed the labeling of the speed. In experiment III, the interaction between size and speed was tested. Results indicated that if the size and the speed of a rolling ball are varied simultaneously, listeners generally are still able to identify the larger ball, but the judgment of speed is influenced by the variation in size. An analysis of the spectral and temporal properties of the recorded sounds listeners may use in their decisions suggested a conflict in available cues when varying both size and speed, which is in line with the observed interaction effect.