Explanation :
Loudness is defined as how our ear perceives the sound. It is basically related to the intensity of a sound wave.
When the same pitch is played louder, its amplitude changes. Amplitude is the maximum displacement covered by a wave.
This is the only difference between the loudness to that of shrillness. The amplitude of the loud sound is more as compared to that of shrill sound.
So, the correct option is (d).
