How does a radio convert radio waves into sound?

Answer 1

The simplest radio is AM (amplitude modulation) radio which modulates a carrier frequency's amplitude in order to convey the sound...it sort of superimposes the desired sound (a song, voice, etc) onto the electromagnetic wave. In order to receive it, an antenna of proportions similar to half of the carrier frequency wavelength is used along with an LC circuit to tune the radio receiver to the carrier frequency which contains the modulated signal of interest. The received radio signal which is composed of the higher frequency carrier and the lower frequency signal (song) is passed through a diode (cat's whisker in crystal radio teminology...also could be a crystal material). Diodes only conduct electricity in one direction. The diode along with a capacitor after it acts to strip off the carrier frequency (because only one half of each carrier cycle is allowed to pass through the diode and charge the capacitor). This "demodulates" the received signal so that only the desired signal remains. In a crystal radio, this demodulated signal is passed to a high impedance earphone which has a ceramic or quartz crystal in it which bends in proportion to the sound frequency left after the diode and capacitor demodulator. The ceramic or quartz crystal bending produces sound waves which we hear as the received signal (voice or music). Other radios will amplify the received signal first and then drive a speaker which moves proportionally to the signal to create sound.

Hope this helps!!

Answer 2

You could always read this:

http://electronics.howstuffworks.com/radio.htm