Sound and Vibration
Something moves back and forth, the air around it moves too, and your eardrum copies that movement. Do it regularly enough and fast enough and your brain stops hearing a flutter and starts hearing a note. The whole of music theory sits on top of that one fact.
- 20 to 20,000 Hz
- regular = pitch
- doubling = an octave
Where you run into this
- Every instrument
- Every recording
- Tuning
- Acoustics
In short
A vibration has a speed, measured in cycles per second, or hertz. Below roughly twenty per second you hear separate pulses, a rhythm. Above that your ear gives up counting and hears pitch instead. Faster means higher, and the relationship is multiplicative rather than additive: double the frequency and you get the same note an octave up, every time, at any starting point.
The frequency slider is the moment most people stop thinking of pitch as a name and start hearing it as a speed. Sliding from the bottom to the top of the range in one gesture makes the whole of music feel like one continuous thing rather than a set of keys.
How it works
Everything else in this pillar is a consequence of this page. Loudness is how far the movement travels, timbre is what other vibrations are happening at the same time, and tuning is a set of decisions about which speeds to use.
Where you run into this
- The low rumble you feel before you hear it
- A car engine speeding up until the rhythm turns into a pitch
- A string that keeps sounding after you damp the body, and stops when you damp the string
Our own examples
Three demos, all synthesis, no recordings: a tone that slides an octave upward so you hear doubling as a musical distance; a tone that drops below the hearing range so you can find your own floor; and the same frequency played long enough that you stop noticing it, which is the first hint that hearing is not the same as measuring.