Modulation enables low frequency audio signals to be radiated long distances.
This is done by superimposing the low frequency audio signal on the high frequency carrier wave by the process of modulation.

The microphone converts sound waves into electrical signals ( a range of 20 Hz to 20 kHz).

These signals are amplified by the audio frequency amplifier.

The carrier frequency is generated by the radio frequency oscillator.

The audio is superimposed onto the carrier by the modulator.

The low power modulated carrier is boosted in amplitude by the radio frequency power amplifier.

The aerial produces an electromagnetic wave which is radiated into space.