This is an npub encoded as audio tones, overlaid on existing audio.

Had a discussion with #[0] today and have spent the last couple of hours creating a service where a creator can upload their mp3 file of a podcast or song, and when someone pays for it the buyer's npub is encoded into the audio stream so that if it leaks everyone knows who did it.

It's loud here to demonstrate it, but will be quiet and at a frequency that still goes through the MP3 compression, but imperceptable when you listen to it. It can't be removed without destroying the audio.

Anyone will be able to use the tool I wrote to decode the npub embedded in the audio, bringing unbearable shame to whoever leaked it.