Effects of ambient noise on time estimation by humans

10 male and 10 female undergraduates were asked to estimate 5-, 10-, 15-, and 30-sec. intervals under five intensities of ambient noise (50, 60, 70, 80, and 90 dB). Interval estimates became shorter as the intensity of noise increased from 50 to 80 dB but became longer at 90 dB. The effects of intensity of noise were most prominant in the two longest intervals. These results are interpreted in terms of CNS arousal theory.