Objects are visible when light rays that are emitted or reflected from them reach the eyes of the person.
Since there is no light in a dark room, no light reaches the eyes of a person.
Thus, we are unable to identify an object or another person in a dark room through a sense of vision.
Sense of hearing:
Since a person cannot be identified in a dark room through the sense of vision, we need to rely on other senses. Thus, we use the sense of hearing.
The pitch, loudness, and amplitude of sound can be the same for two different persons, but the quality of sound, also known as timbre, is always different for every person.
Timbre can never be the same for different persons, just like fingerprints. It is the characteristic that helps differentiate the sound of the same pitch and loudness.
Thus, a person can be identified in a dark room through the timbre of sound.