what term describes the human perception of frequency
Loudness The perception of loudness is related to sound pressure level (SPL), frequency content and duration of a sound. The human auditory system averages the effects of SPL over a 600–1000 ms interval. A sound of constant SPL will be perceived to increase in loudness as samples of duration 20, 50, 100, 200 ms are heard, up to a duration of about 1 second at which point the perception of loudness will stabilize. For sounds of duration greater than 1 second, the moment-by-moment perception of loudness will be related to the average loudness during the preceding 600–1000 ms.[citation needed]