Spectral cipher
Hide an image inside a WAV file. It appears only in the audio’s spectrogram.
How it works
What it does
Spectral cipher draws a picture into sound. It turns an image into a WAV file that sounds like noise, but when you open the audio in a spectrogram viewer, which plots frequencies over time, the picture appears. The reveal mode does the reverse and extracts the image from such a WAV file.
A musical trick
Musicians have hidden images in spectrograms for decades. Aphex Twin put his own grinning face into a track on the 1999 Windowlicker single, Nine Inch Nails hid images in the Year Zero album in 2007, and Mick Gordon tucked pentagrams and the number 666 into the 2016 Doom soundtrack.
How it works
The image is resized to 512×512 pixels and turned to grayscale. Each column becomes a short slice of sound of about 46 ms, and each row becomes a frequency between 300 Hz and 14 kHz whose loudness follows the brightness of the pixel. The result, about 24 seconds long, is mixed into a carrier track; the strength slider sets how strongly the image stands out against it.
Good to know
This is a hidden picture, not encryption. There is no password, and anyone who opens the file in a spectrogram viewer such as Audacity will see the image. Use it for puzzles, art and fun, not for secrets. MP3 and AAC compression, resampling or trimming the start can blur or shift the image, so share the WAV as it is. Everything runs in your browser.