It's a simple image liked to a specific audio file.. You see when the artist boldened the waveform and made it darker.. That alone can mess up all audio information might be on it and it's no longer an sound wave form..
Smart trick anyway.
May as well tattoo a bar code that links to an online recording - but if youre carrying a phone in order to decode it, why not just keep the recording on your phone? Am I taking this too seriously? Is it a joke?
I don't know why people deceive others by publishing false videos on YouTube and tell people it is an audio signal.. It's not. Download the image and stretch it and you wouldn't see the audio some wave. May be the app has image recognition then plays the linked audio file corresponding to that image.. But to fake the timeline movement along the image and tell people it's the audio wavefonm.. I think that's not right.