Low-frequency source characterization of aircraft noise during landing operations.

Low-frequency noise emission by commercial aircraft is of particular interest due to the minimal attenuation of these frequencies by barriers and atmospheric absorption. Furthermore, noise modeling software such as the Integrated Noise Model (INM) does not currently model noise emissions below 50 Hz. The current study characterizes source noise during landings to facilitate more-accurate modeling of community impact. Recordings of aircraft landing operations were made with a widely spaced microphone array positioned near and parallel to the 19R runway at Washington-Dulles International Airport in October 2004. In addition, the landings were recorded with a video camera to obtain positional data of the aircraft. Given an aircraft's position and velocity along the runway, the signal at each microphone is corrected for retarded time, spherical spreading, atmospheric absorption, and Doppler shift. Individual microphone signals are combined to determine level and directivity overall and in third-octave bands in the INM frequency range 50 Hz - 10 kHz, and to calculate spectra at lower frequencies (10 Hz - 63 Hz). Aircraft studied ranged from regional (e.g. Bombardier CL600) to highcapacity, long-distance jets (e.g. Airbus 330). Results for the Boeing 777 and the Airbus 320 are presented here.