To conduct noise assessments of ACMV (air conditioning and mechanical ventilation) systems under NEA's guideline for TOP submission, each test point is tested for a 15 minutes equipment "ON" and another 15 minutes "OFF" state. As it would take time to switch equipment on and off, each point usually take about 45 mins to test. That is assuming a one-take measurement, and external factors such as a sudden event of airplanes, mo...