Category: 10 Superposition

10.9.4 More Demonstrations

The pressure nodes and antinodes of a standing sound wave can be revealed via different means.

The Kundt’s Tube demonstration uses hopping Styrofoam beads…

and the Ruben’s Tube uses flames!

explanation at xmdemo

10.10 Musical Instruments

Can you differentiate between the sounds of sinusoidal, saw-tooth and square waves? Only the sinusoidal wave is monotonic. It truly consists of one single pitch. The saw-tooth and square waves are actually the superposition of many sinusoidal waves of different frequencies. So they contains higher harmonics on top of the fundamental. While they all sound like the same pitch to us, they also sound different because of the different (amplitudes) of the harmonics they contain.

The sound produced by the guitar (string) and the recorder (open pipe) are also not monotonic. It takes a bit of imagination to realize that the standing waves formed on the string and the air in the pipe actually consists of many frequencies at the same time. But that’s what allows the sound produced by different instruments to have different timbres.