Sine Wave
Sine Waves and Pitch Measurements |
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The air around us is constantly in motion, sometimes behaving like choppy seas, other times like a still pond, still other times like great waves. Sound is how our ears sense motions of the air. Musical tones are regular or periodic motions of the air similar to the even ripples a stone makes when dropped into a still pond.
The simplest musical tone is a sine wave. It consists of regular waves of sound at regular intervals. When graphed, a sine wave looks like this:
Every time this wave goes down then goes up again it completes a cycle. High pitched sounds have a very short wave-length - their graphs go up and down very quickly. Low sounds have long wave-lengths - their graphs go up and down slowly. The frequency of a tone is measured in cycles per second.
Use an interactive Sine Wave Applet to discover what happens when sine waves interact.
When talking about microtonality it is convenient to use a measurement called cents. Cents divide the notes on the piano into 100 equal divisions each. There are 100 cents in a half step, just as there are 100 cents in a dollar. Since there are 12 half steps in an octave, there are 1200 cents in an octave. Using this system we can speak of notes being 16 cents flat or 12 cents sharp. Many modern digital tuners display cents very accurately.
The less familiar but sometimes more useful musical measurement is Hertz, which stands for "cycles per second" and measures regular motions of the air over time.
An explanation of the tone quality of string and woodwind instruments.