Additional Info

• ID Code: H1-25
• Purpose: Measure the speed of sound by determining the travel time of a pulse between two microphones.
• Description: A loudspeaker sends pulses past the two microphones, and the oscilloscope displays the pulses on its time axis. The oscillator is set for 2 Hertz square waves 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. In the photo above the microphones are 34.5 cm apart and the scope is set at 200 microseconds/div.

  For a simpler calculation, you can preselect the spacing of the microphones to give a convenient time delay, such as 1ms.

  Note that this demonstration does not reliably give results as accurate as demonstrations such as H1-21, but the simpler setup can be useful in some classes. One option can be to use multiple methods, and invite students to discuss the differences between results.

• Availability: Available