What pitch actually is
A sound is a pressure wave, and its pitch is how many of those waves arrive each second. Change the frequency and watch the humps crowd together while the wavelength beside it shrinks.
What pitch actually is — the interactive part
Both waves travel at the same speed. The top one is the note you set; the bottom one is fixed at A2, 110 Hz, to compare it against.
- Wavelength in air
- 1.56m
- Octaves above the reference
- 1.00
What this scene shows, in words
Both waves travel at the same speed. The top one is the note you set; the bottom one is fixed at A2, 110 Hz, to compare it against.
- The note you set — a wave with 2 cycles across the stage and a height of 26, travelling.
- A2, 110 Hz — a wave with 1 cycles across the stage and a height of 18, travelling.
The values above change as the scene plays and as you move the controls; they are read out again whenever it is paused.
Wavelength in air is 1.56 m. Octaves above the reference is 1.00.
Pitch is a count, not a size
Sound travels through air at about 343 metres per second whatever its pitch. So a wave that repeats more often has to be shorter: 110 Hz is a bit over three metres from one crest to the next, and 880 Hz is under half a metre. Nothing is moving faster — the same speed is simply divided into more repeats.
Loudness is the other axis
Height and frequency are independent, which is why they get separate sliders. Making the wave taller pushes the air further each time and the sound gets louder; the note does not change. That is why a whisper and a shout can be the same note, and why a violin and a tuba playing the same pitch produce waves that repeat equally often but look nothing alike.
Drag Loudness from end to end and watch the wavelength readout not move at all — the humps get taller, not closer together.
Check your understanding
A singer holds one note and gets louder. What has changed about the wave?
Pick one to check yourself.