An environmental noise monitor has been designed, constructed, and tested for the U. S. Environmental Protection Agency. The system includes a Brüel & Kjaer 4921 outdoor microphone system, a Wang 600-14 computing calculator as the digital controller and statistical analyzer, and a Nagra SJ tape recorder for analog recording. The system has a 80-dB dynamic range and is capable of separately classifying data acquired during the period of time in which the winds are above a preset value. The digital system constructs variable length blocks of data. For each block various L levels as well as Leq are calculated. Running totals are kept of the daytime and nighttime Leq and each 24 hours a new Ldn is calculated. By using 3-hour blocks, the system can run unattended for a week at a time. Because the calculator is part of the system, results are always immediately available in the field.