The effects on perceived noisiness of spectral and temporal combinations of stimuli at varying durations were determined by 20 college students in an anechoic chamber. Several recordings of turboprop, turbofan, turbojet, and helicopter flyovers were also included in the list of stimuli. The results indicated that the most accurate predictor of the judged noisiness was perceived noise level with tone and duration corrections as outlined by the Federal Aviation Administrations (1968) aircraft certification procedure. To illustrate the responsiveness of effective perceived noise level (EPNL) over perceived noise level (PNL) in predicting the noisiness of stimuli, the results of the duration test revealed that, at judged equal noisiness, 75% of the data were within 4 dB of the standard signal for EPNL with the FAA tone and integrated duration measure as compared to 11 dB for PNL.