Amplitude modulation (AM) is a
modulation technique used in electronic communication, most commonly for transmitting information via a
radio carrier wave. In amplitude modulation, the
amplitude (signal strength) of the carrier wave is varied in proportion to the waveform being transmitted. That waveform may, for instance, correspond to the sounds to be reproduced by a
loudspeaker, or the light intensity of television pixels. This technique contrasts with
frequency modulation, in which the
frequency of the
carrier signal is varied, and
phase modulation, in which its
phase is varied.