Auditory perception of the size and velocity of rolling balls

In everyday life a complexity of sounds provides us with information about sound sources, their locations, and their surroundings. In the interaction with systems in their environment, this wealth of information may be of use to the user. In order to create suitable auditory interfaces we require a better understanding of how people perceive everyday sounds. We have chosen to study the sounds of rolling balls, because a rolling ball can be used as a metaphor for cursor movement resulting from moving a mouse or a trackball. In three experiments the perception of recorded sounds of rolling balls was investigated. In the first experiment subjects were presented with pairs of sounds of rolling balls with different sizes and equal velocity in which they had to decide which of the two sounds was created by the larger ball. In the second experiment the velocity of rolling balls was varied and subjects had to choose the faster of two balls equal in size. The results showed that subjects are able to identify the size of rolling balls and that most subjects can clearly discriminate between rolling balls with different velocities. However, some subjects had difficulties in labelling the velocity correctly, probably due to lack of feedback about the correctness of their responses. In the third experiment both size and velocity varied. The results showed a clear interaction between the auditory perception of size and velocity of rolling balls.