This is a technical question about sound, microphones, and cellphones. I am baffled that sound emanating from my phone's speaker is inaudible to someone I'm talking to on the phone. If i can hear music from my phone, the same music should be picked up by the mic that I'm speaking into. But it is as if the music is completely absent, not just softer. The only way i can figure is that there's a digital "negative sound" signal that erases exactly the music that the mic is picking up before the signal leaves my phone as radio waves. Is that right?