Frequency modulation
In telecommunications and signal processing, Frequency modulation transmits information over a carrier wave by varying the frequency. This technique is different from amplitude modulation which varies the amplitude, but keeps the frequency constant. In the context of broadcasting radio signals, Frequency modulation is often shortened to FM. When transmitting analogue sound, the sound quality of FM signals is better than that of amplitude modulation (AM) signals. However, FM signals do not travel as far as AM.
Many radio stations send out both kinds of signals, reserving AM for talk shows, and FM for music. In addition, FM is usually sent as two signals (with one signal's frequency a little lower than the other), which can come to two different speakers in a home. This creates FM stereo sound.
