The petrochemical plant studied in this study is located at an altitude of roughly 2.200 meters from the sea level. Eleven buildings are dispersed over an area of 40.000 m(2). The average temperature in January is -11,4 degrees C and 16,3 degrees C in July. 92 employees work in a shift system (14 days "On" - 14 days "Off") in the plant. Measured L-eq values were in the range of 81,2 to 110,2 dBA. Workplace Index (WPI) was (2,9 / 5,0).