We introduce a new method of determining the coefficient of restitution (COR) of a ball-surface combination by using the sound produced by the impact/collision of the ball with the surface. Using a digital electronic circuit, the electrical signal is amplified and fed to a digital storage oscilloscope through a relay circuit for measuring the time interval between two successive collisions of the ball with the surface. This time interval is then used to determine the COR. (Contains 5 figures.)