Modulation is a process in which the audio signal having very low frequency is put on a sine wave having frequency higher than that of the audio signal.
The equation which represents the sine wave is given below:
In the above equation E represents the maximum voltage and instantaneous voltage at a particular instant of time (t). It is denoted by e. Without modulation audio signal can’t reach to longer distances because the energy of the audio waves is too low. Energy is represented by the relation
Other main reason of modulation is that the audio signals are of less frequency, Due to less frequency range lot of disturbance will take place in the signal.