A- If the sound of a caller is broadcast by a station and then comes out of his 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 7-second broadcast delay some stations use to avoid foul language or slander being aired. If such system is in use and the caller can hear his radio, he will hear himself 7-seconds ago while trying to have a conversation in the present. Obviously this will be a very off-putting.