spectrogram
your microphone, drawn as frequency against time. whistle and you get a clean line. speak and you get stacked stripes — those are the harmonics your vocal cords make, and the shapes they slide into are vowels. clap and you get a wall, because a click is every frequency at once.
110 Hz
220 Hz
440 Hz
880 Hz
1.76k Hz
3.52k Hz
7.04k Hz
loudest frequency
—
nearest note
—
level
try humming a steady note and sliding it up — the line bends, and you can watch the harmonics above it bend in parallel, always at exact multiples. that parallel motion is why we hear it as one sound and not a chord.
the vertical axis is logarithmic — every gridline is one octave, a doubling. a linear axis would squash everything musical into the bottom sliver.