idea
Vibration and pitch
Every sound starts with something moving back and forth: a violin string, a clarinet reed, the air inside a flute, your own vocal folds. The number of times it moves back and forth each second is its frequency, measured in hertz (Hz). We hear frequency as pitch. The A that orchestras tune to moves 440 times a second, and the A an octave below moves 220 times. When you pluck a string the sound gets quieter as it fades, but the pitch stays the same, because the string keeps the same rhythm while its movement gets smaller.