GAIA Exploring Sound (PDF) - Roland Corporation Australia

Frequency
Let’s re-phrase that. Firstly, as you played higher notes the waves
appeared “more frequently!” Would that suggest that higher notes
“have a higher frequency?” Of course!
Secondly, each octave was an exact multiple of the first. Move up
an octave and you’ve doubled the frequency. Move up two
octaves and you’ve multiplied the frequency by 4. Exciting?
To put that as a simple calculation, each time you move one
octave higher you double the frequency of the waveform!
By the way, we measure frequency in cycles per second. That is,
if a tuning fork vibrates 440 times in each second we say it is
vibrating at 440 cycles per second. We also use a specific name
for this; the Hertz, named after a German physicist, Heinrich
Hertz. 440 cycles per second equals 440 Hertz (or 440Hz for
short).
You have now seen, and can clearly understand, why we speak of
musical notes of a higher, or lower, frequency. Why we say that
musical notes have a mathematical relationship with each other.
This is good stuff!
Perhaps we have jumped a little too far ahead. We were talking
about Pitch and Wave Shapes. Let’s just concentrate on the Pitch
controls to begin with....
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