This dual purpose apparatus provides a compact facility for the measurement of the velocity of sound in air and also for the analysis of standing waves. It requires an audio signal generator and a dual beam oscilloscope (not included). A phase measurement between the speaker and microphone signals is made on an oscilloscope. The distance required to traverse through a 360° phase shift is noted. Knowing the frequency and distance, the speed of sound is computed. With the reflector in place a standing wave can be generated. Nodes and antinodes can easily be seen from the amplitude variations on the CRO.