Serc: Investigating Sound: Using Open Tubes to Demonstrate Beat Notes

For this interactive demonstration, students will observe while the teacher creates two sound frequencies using open tube resonators of nearly identical length. The nearness in length produces two slightly different frequencies which interfere with each other to produce a beat note Beat notes are used by musicians to tune instruments. Frequencies that differ by less than 7 Hz can be detected by the human ear. The frequency of the beat note is equal to the difference between the frequencies of the two sound waves.