Concepts

Interference and diffraction of sound

Overview

Function generators drive two speakers placed in front of the class. The students cover one ear and slowly move their heads around to hear the interference pattern.

Details

Equipment

• [1] Function generator
• [2] Speaker
• [1] Metre stick

Classroom Assembly

1. Plug in and turn on both function generators.
2. Set the amplitudes to a minimum.
3. Set each function generator to produce a 1000 Hz sine wave.
4. Place the two speakers about 1.2 m apart.
5. Connect a function generator to both speakers.
6. Activate the function generator outputs and slowly increase the amplitude to the desired level.
7. Turn off the outputs.

Important Notes

• In large classrooms, the approximate distance the students' head must move to go from high amplitude to low amplitude is longer.
• If the speakers are too close to each other, the distance between nodes and crests is too large.
  

Script

1. Turn on the function generator outputs.
   
2. Instruct the students to plug one ear and move their heads from side to side.
3. Have the students approximate the distance between region of high amplitude and low amplitude.

Additional Resources