Authority. Transportation Article, §5-805(a), Annotated Code of Maryland, authorizes the Executive Director, by regulation, to establish methods for the calculation or measurement of cumulative noise exposure values. Noise Rating. The noise rating for description of exposure to aircraft noise shall be the day-night average sound level (Ldn). Development of noise contours of equal noise exposure are to be determined using a prediction method in accordance with the procedures of §D, below. Measurements, undertaken in accordance with the procedure of §E of this regulation, may be used to confirm the locations of contours of equal noise exposure. Prediction Method. Contours of equal noise exposure in terms of the day-night average sound level are to be prepared using a procedure designed to develop Ldn contours based on data as described in this section. The use of a particular procedure is subject to the approval of the Executive Director. Data Base. The following information is required to develop contours of equal noise exposure: Map location and dimensions of all runways and the airport property line at a scale specified by the Executive Director. Map location of landing threshold and start of takeoff roll for each direction on each runway. If there are several thresholds or start-of-roll points corresponding to different types of aircraft, these shall be noted with a clear description of the relevant aircraft types. Map locations of engine runup and maintenance areas within the airport property. Map locations of flight tracks or descriptions of departure procedures for all arriving and departing aircraft and for traffic patterns, if any. If there are different flight tracks or procedures associated with different types of aircraft, these shall all be included. The scales of any maps shall be as specified by the Administration. Special flight procedures or restrictions, including, but not limited to, airspace management, curfews, and noise abatement procedures. Effective annual average daily numbers of flight operations by type of operation (landing, takeoff, touch-and-go), by aircraft type, by gross weight for takeoffs, by runway, by flight track, and by time of day. Annual average daily number of engine maintenance runups by type, by duration, and by time of day (daytime or nighttime). Flight profiles for arriving and departing aircraft. The relationship of aircraft sound level to the distance between the aircraft and the ground location, by aircraft time and operation. Measurement Method. Noise Measurement System Requirements. The system for the measurement of noise exposure shall provide the hourly sound level for each hour of the day, together with identification of the hour, and the measurement location. The overall accuracy of a noise measurement system shall be +=/-1.5 dB. The system shall be of a type approved by the Executive Director. Measurement Requirements. Measurement Conditions. Measurements shall be made when aircraft operations occur that affect the location being studied. The number of 24-hour measurements of Ldn shall be equal to the value given in the table below, depending on the data range in decibels for the set of measurements. For this purpose, the data range shall be determined from the field measured noise data. Noise measurements shall be continued at each location until the requirement of this article is satisfied.