The loudness of a sound wave is given by the amount of energy that the pressure wave carries and it is measured in decibels (dB) which is the relative intensity of the pressure wave of a sound to the standard pressure
A loud sound has a high amplitude and a soft sound has a low amplitude, such that as the amplitude of the sound is increased, due to increased energy input, the sound becomes louder, and as the amplitude of the sound is decreased due to reduced energy input, the sound becomes softer.
