When placed on a flat surface, the stack redirects the waves such that reflected waves are exactly as they would be if the stack were not there at all.

BBC: Acoustic 'cloaking device' shields objects from sound

That is because the radio waves produced by each phone are reflected off the metal walls of the carriage, bus or lift.

ECONOMIST: Are mobiles phones on trains dangerous or not?

Five- to 7-foot waves tailor-made for contemporary kayaks kept the crew entertained as they reflected on their journey.

CNN: Moroccan multisport