Spectrogram

What it's for

Turn text or a picture into a sound that draws it in a spectrogram, a chart of which frequencies a sound contains over time, and draw the spectrogram of any sound. Musicians have hidden pictures in their tracks this way, and audio puzzles often do too.

For example, when a puzzle gives you a strange-sounding audio file, open it under See a sound’s spectrogram to look for writing.

How to use it

Under Draw into a sound, type text or choose an image (or drop one on its box), then the length and the range of frequencies to draw in (remembered), and choose Make the sound. Bright parts become loud tones; tick Dark parts are loud for a dark drawing on a white background. You can play the sound, download it as a WAV, and see its spectrogram below.

Under See a sound’s spectrogram, choose a sound file (WAV, MP3 and most others the browser plays) and the highest frequency to show. Time runs left to right and frequency bottom to top; louder is brighter.

Example

Keep the text as:

HELLO

and the default 5 seconds from 2,000 to 10,000 Hz, and choose Make the sound. It sounds like a hiss, and the spectrogram shows HELLO in orange and yellow.

Good to know

Text is drawn up to 80 rows high and images 96 rows, between 1 and 30 seconds. Compressing the sound to MP3 or AAC can blur or remove the highest frequencies, so keep drawings below about 15,000 Hz if the file will be converted. Sounds over 10 minutes aren’t drawn. Loud sounds near the drawing’s frequencies hide it.