Silent Burn-in Audio - Burn-in quietly while canceling sound 

If you have given up on burn-in speakers because of the installation environment or neighborhood nuisance, why not try this sound?
This sound uses the same principle as noise-canceling headphones to quietly improve the sound quality of speakers.
🔊 Setting
First, play a song you normally listen to, not the one in this video, and set the volume to a level that makes it seem a little loud. After setting, stop the music. (If you set the volume too loud, the risk of failure increases, so moderation is the key.
Place the speakers facing each other. For models without speaker guards, leave a space of a few millimeters to a few centimeters.
Play the video. The sound is cancelled and the speakers are shaking but the sound should be quiet.
The output is inaudible to the ear because it starts at an inaudible frequency, but it is still being output.
Please be careful never to turn up the volume. It is OK to turn it down.

Видеоклипы