Purpose: To demonstrate (1) beats, and (2) interference using sound waves.

Self contained audio oscillators mounted at opposite sides of a rotatable platform.

Beats: Two units (each consisting of an audio oscillator, power amplifier, and speaker) are used to demonstrate beats. The packages are self-contained and all you need to do is plug them in and turn on the power to the audio oscillators. The power control for each unit has been wired through the audio oscillator off/on switch. Make certain the audio generators are set on sine wave instead of square wave or you will get junk.

The best frequency response for this system seems to be between 300 and 1000 Hz. Set one oscillator on about 700 Hz and adjust the other to about 700 Hz; behold, just as expected, beats.

Interference: To demonstrate interference, turn off one oscillator and disconnect that speaker from its power supply by disconnecting the jumper wires between the "A" and "B" jacks on the back of that speaker enclosure. Use the long leads supplied to interconnect the "B" jacks between the two speaker enclosures. (Observe color coding.) Adjust Unit B to about 700 Hz with the volume all the way up. Have the students cover their left ear and turn their right ear toward the speaker. Now, have them move their heads back and forth about a half meter and they should detect maxima and minima.

References:

Manual: None