TOK physics: Music
Knowledge questions
Can knowledge in one area be used in another?
Does the fact that two different phenomena share the same model make them the same?
What is the difference between perception and measurement?
Does knowledge of the physics of music enable you to play better?
Does an understanding of the physics of sound enhance your appreciation of music?
Sound is a wave, this means it is made of a series of oscillations that are out of phase with each other, like when a wave goes round a stadium.
Each line of spectators stand a bit after the ones to their left. This is actually a pulse, to make a continuos wave they would have move up and down like these pendulums.
The frequency of the wave is the number of complete oscillations of one of the points per second.
The first thing to be named a wave was a water wave, when a stone is dropped into a lake the wave spreads out.
When you clap your hands in a room the sound spreads out. The way the sound spreads out is very similar to the way a water wave spreads out, in fact we can use the same mathematical model for both even though the air moves back and forth whereas the water moves up and down.
Can you see how this is also made of a series of out of phase oscillations.
The equation is:
Because they are so similar we call them both waves.
The frequency of a sound wave is related to its pitch. Pitch is something we sense, frequency is something we measure, it is a physical quantity with units Hz of s-1. Pitch is represented by a letter ABCDEFG. Here is a table showing the frequency of the different notes.
A note of frequency 880 Hz is also an A but it has twice the frequency. In terms of physics these are completely different frequencies but the same note. The musical scale is based on what sounds good not physics. When it was introduced there would have been no way of measuring the frequency but frequency of the notes are related.Each note is 1.0595 times the frequency of the one before. This is the 12th root of 2 so the next note in the series will be:
1.0595 x 1.0595 x 1.0595 x 1.0595 x 1.0595 x 1.0595 x 1.0595 x 1.0595 x 1.0595 x 1.0595 x 1.0595 x 1.0595 x 440 = 880Hz
This is 1 octave above 440 Hz
If the musical scale was based on physics it might be something more regular like this:
Below is a simple musical instrument with the physics scale and the music scale. Try playing music on the physics scale. if you are a musician you can also show off your talent by playing something on the music scale. The sounds might not play in all browsers, it it doesn't work try firefox.