Bouncing Ball Explorer

Analyzes and models audio recordings of a ball bouncing on a hard surface.

An accessible experiment in mechanics entails exploration of the sound of a bouncing ball dropped on a hard surface, the sound recorded with a mobile phone or laptop microphone. For one-dimensional motion over a limited range of collision speeds and in the absence of air drag, inelastic energy loss reduces the ball speed in each bounce by a nearly constant fraction called the coefficient of restitution (COR) which depends upon the constitution of the ball and of surface. The coefficient of restitution is the ratio of speeds in successive bounces and equal to the ratio of successive loft times.

The script Bouncing Ball Acoustic Analysis analyzes several provided recorded sounds of a bouncing balls and may be used to analyze other such files. It introduces acoustic signal processing in MATLAB and several signal analysis techniques (spectral analysis, filtering, and cross-correlation) in finding the bounce times, and examines the validity of the COR model. For light balls, air drag mimics a speed dependence to the COR. The script Bouncing Ping Pong Ball Analysis models this effect.

The scripts may be of interest to students and teachers of computational physics. 'Try this' suggestions are included for further exploration.