Which modulation technique modifies the frequency of a carrier wave?

Frequency Modulation (FM) modifies the frequency of a carrier wave to encode information. This technique involves varying the instantaneous frequency of the carrier signal in relation to the amplitude of the input signal or audio. As the input signal's amplitude changes, the frequency of the carrier wave shifts accordingly, producing a waveform that represents the original signal. This is particularly effective for reducing noise and providing a clearer transmission in communication systems, making FM widely used in broadcasting, particularly for music and voice transmissions.

Other modulation techniques function differently, with amplitude modulation changing the strength of the carrier wave while pulse modulation involves discrete signals. Phase modulation also varies the phase of the carrier but not its frequency.