Introduction to National Airport Noise Footprint Simulator
(Notice: Because of new security measures with java applets, some browsers may filter out the java applet, so this page may not work for you. However, it stills works on Apple's OS 10.6.8 or eqivalent PC operating system.)
You initiate a flight out of National Airport by clicking the Take Off button. Flights move northwest up the Potomac River (default direction) until they reach the edge of the map, or until you click the Erase Flight button. Clicking the Erase Flight button twice resets the altitude to zero.
A flight is represented by the intersection of its noise bubbles with the surface of the earth.
A black disk shows where the flight is heard at 55 or more decibels. The airplane's noise is a noticeable presence throughout the blackened area.
A purple disk shows where the flight is heard at 65 or more decibels. The airplane's noise disrupts conversations and thought within this area.
A red disk shows where the flight is heard at 75 or more decibels. In this region the noise distresses people.
A yellow disk shows where the flight is heard at 85 or more decibels. Bodily harm can result from the noise in this region.
You can adjust factors influencing surface sound by adjusting scrollbars at the right of the map. National Airport "North Operations" is the default direction (shown as 328 degrees Northwest). "South Operations" can be seen by adjusting the Direction scrollbar towards the right end to 190 degrees. Flights departing up the Anacostia River can be viewed by setting the Direction scrollbar towards the left side to 48 degrees Northeast. Showing what the sound footprint is for different types of aircraft can be seen by setting the Engine Noise scrollbar to the values shown below.
Engine Noise - the decibel level measured 450 meters from the source (FAA standard). Some original Stage 2 aircraft have been modified for Stage 3 certification. Those which are in both categories are: 747, DC-10, 727, 737, DC-9, and MD 80. Their official sound take off levels run from 100 dBEPN(Effective Perceived Noise) down to about 84 dBEPN depending on whether they are Stage 2 or Stage 3, and their individual configuration. Some Stage 3 "quiet" aircraft are: 757, 72 dBEPN; 767, 82 dBEPN; A320, 71 dBEPN; MD 90-30, 71dBEPN; 737-400, 80 dBEPN; and Canadair RJ/CL600, 67 dBEPN. Although reported landing moise levels are often listed as greater than departure noise (sometimes by as much as 15 dB), that occurs because of the way the FAA measures take-off and landing noise levels. Take-off noise is normally greater, and that is the reason CAAN uses only a departure simulator. Since this information was written some years ago, many of the above listed stage 2 planes have been removed from American service.
Direction - the flight path specified on a 360-degree compass.
Climb - the plane's rate of climb in degrees. (Altitude is reported here during a flight.)
Speed - the plane's airspeed in miles per hour (aircraft normally use knots instead of mph).
Another scrollbar - the Time Multiplier - adjusts the extent to which the simulation is faster than life. The pace can be set at real time by selecting a 1:1 multiplier.
Results are approximate since additional factors (like weather and sound frequency) affect how noise travels. Nevertheless the simulator provides insights concerning airplane noise, and what remedies would be most effective at a particular location.
This interactive aircraft noise simulator comes to you courtesy of Save Our Sky in Indianapolis, IN. SOS is now off the "air."
