Turn Down Your Radio Please

Why do all presenters of radio phone-ins ask callers to turn their radios down? If the sound of a caller is broadcast by a station and then comes out of his/her radio and back down the phone to be broadcast again, it creates a loop. A complex noise, such as voice , is made up of various sound waves of different frequencies that, on their own, sound like single whining tones. In a loop, one such frequency can become more prominent than the rest and as it is repeated it will overlay itself, getting louder and louder, until it's distinctly and unpleasantly audible. A second reason for turning your radio down is the seven second broadcast delay some stations use to avoid foul language or slander being aired. If such a system is in use and the caller can hear his radio, he will hear himself seven seconds ago while trying to have a conversation in the present. Obviously this will be very off-putting.