The effects of ambient noise on Distortion Product Otoacoustic Emission(DPOAE) measurement were systematically examined in 20 normally-hearing adults as a function of averaging time and test frequency. 2f₁-f₂ DPOAEs were measured at nine ambient noise levels from the baseline to 65dBA. For each noise level, measurements were made at four different averaging times for 0.7-6kHz. Findings indicated that, to achieve a preselected DPOAE-to-noise ratio (D/N) for DPOAE presence, longer averaging times were required as noise level increased and as frequency decreased. In most cases, the minimum D/N value required for 95% specificity increased as averaging time and frequency increased ; however, as noise level increased, the vlaue decreased. Results also indicated that noise levels of 40-50dBA affected D/N considerably in the low frequencies. In the high frequencies, however, even 60-65dBA of noise did not affect the D/N. It is suggested that (1) for reliable and efficient DPOAE measurement, test frequencies, especially below 2kHz, be selected carefully considering the ambient noise level and spectrum in a testing site and appropriate averaging time be used, and (2) criterion value for normal response be selected considering parametric factors such as ambient noise, averaging time and frequency.