Determining the velocity of sound in solids

The object of the experiment P1.7.3.5 is to determine the velocity of sound in aluminum, copper, brass and steel rods. This measurement exploits the multiple reflections of a brief sound pulse at the rod ends. The pulse is generated by striking the top end of the rod with a hammer, and initially travels to the bottom. The pulse is reflected several times in succession at the two ends of the rod, whereby the pulses arriving at one end are delayed with respect to each other by the time Δt required to travel out and back. The velocity of sound is thus

To record the pulses, the bottom end of the rod rests on a piezoelectric element which converts the compressive oscillations of the sound pulse into electrical oscillations. These values are recorded using the CASSY system for computer-assisted measured-value recording.