It feels your skin. It rests on your skin, and it knows when it is you're talking. And by knowing when it is you're talking, it gets rid of the other noises that it knows about, which is the environmental noises.
Siente tu cutis; se posa en tu piel, y sabe cuando es que estas hablando Y sabiendo cuando estás hablando elimina todos los otros ruidos que conoce, del ruido ambiente.