The treble range contains: presence (4–6 kHz — vocal clarity and instrument definition), brilliance (6–12 kHz — air and sparkle of cymbals, acoustic guitar, and room ambience), and air (12–20 kHz — the sense of space and openness, mostly harmonic overtones and reverb tails).
Treble is the first frequency range to decline with age — most adults over 40 have significantly reduced sensitivity above 15 kHz. Treble is also the most directional frequency range — tweeter height and toe-in angle significantly affect perceived treble balance. An overly bright system causes listener fatigue within 30–60 minutes.