117 This professor bounces sound waves carrying music that can not be heard out loud but can be heard in. (m.youtube.com) posted 336 days ago by GGRockz 336 days ago by GGRockz +117 / -0 43 comments share 43 comments share save hide report block hide replies
Yeah. The wavelength is fairly long - a couple miles long. Unless he was lying about the frequency.
4200 meters.
My bad - we are thinking about RF. Sound in air is different.