Speed Of Sound Between Two Microphones

Purpose

To measure the speed of sound by determining the travel time of a pulse between two microphones.

Equipment

Oscillator, small speaker, two microphones with holders on optical rail, mixer amplifier, and oscilloscope.

Setup Time

10 min.

Images

h1-25

Description

A loudspeaker sends pulses past the two microphones, and the oscilloscope displays the pulses on its time axis. The oscillator is run at 40 Hz to produce well-separated pulses. The speed of sound is the distance between the two microphones divided by the time delay read from the oscilloscope. If the scope is set to 0.2ms/div, the math is simple if you move the microphone so that the two pulses are 5 cm or 1 ms apart.