Duration of sound means length of sound in time. Duration of sound also deals with sound periodicity.
Periodicity is the most useful aspect of duration because it gives beat and rhythm to music.
Periodicity is basic to life. Music can be a metaphor for the life process, especially for its periodic aspects. Much music contains a steady pulse or beat. Faster vibrating objects have higher pitches while slower vibrating objects have lower pitches. Pitch highness and lowness is relative.