Most binaural beat generators on the Internet use two carriers: one for each ear.
Therefore, binaural beats only work through headphones. In order to create a binaural beat, each ear must receive its dedicated signal. When each tone is sent to a different ear, there will not be any physical interaction between the waves, yet your brain still creates an interference inside your head: the so-called binaural beat.
Pure tones played together interfere with each other when they are close in pitch but not identical.