Define the term Amplitude
In simpler terms, amplitude is the amount or relative value of a signal. Amplitude is measured in units of pressure e.g. Newtons/sq. m. But what is physiologically more relevant is power, i.e. (amplitude) 2. The faintest whisper that the ear can hear is much weaker than the loudest sounds that the ear can tolerate without getting damaged. Therefore, if the entire range of intensity of audible sound were to be expressed directly, 'we would be dealing with very inconvenient figures.
Hence, we use a logarithmic scale to measure the intensity of sound. A logarithmic scale, as you know, is a highly condensed sca1e.The logarithm of 1 is 0, and log 1012 is 12, therefore the range from 1-1012 gets condensed to 0-12 on the logarithmic scale.