The quality of a sound is that property by which we are able to distinguish the voice of a particular person or instrument even though they have other factors like loudness to be the same.

Example – By quality of sound, we are able to recognise a male voice and female voice even if they are of the same loudness.

Hence, it is the virtue of which two sounds of the same pitch or the loudness produced by the two different musical instruments or people which can still be distinguished.