Wirebook › Glossary › Spectrogram
What is a spectrogram?
In one sentence: A picture of sound with time across, pitch up the side and loudness as brightness, so a tune shows up as bright lines.
A little more
A spectrogram is made by cutting sound into short slices, a few hundredths of a second each, and measuring how strong each frequency is in every slice (usually with a maths step called a Fourier transform). Lined up side by side, the slices make a picture: time runs across, frequency (pitch) runs up, and colour or brightness shows loudness.
Speech shows up as bands that shift as you change vowels, a whistle as a single thin line, a drum as a tall stripe. Spectrograms are used for song recognition, speech recognition, studying birdsong, finding faults in machines and in audio compression, which drops the parts of the picture our ears are least likely to notice.
See it in action
- BonusHow does a phone know a song from hearing it?Hold up a phone in a noisy shop and it names the song in seconds.8 min · interactive
- BonusWhy does a video call go blurry when the connection is slow?Dial a pretend video call's bandwidth thinner, spend a tiny 10-bit budget on eyes vs mouth vs wallpaper to still read a facial expression, then reveal the clear face.7 min · interactive