Annoyance Caused by Aircraft En Route Noise

A laboratory experiment was conducted to quantify the annoyance response of people on the ground to en route noise generated by aircraft at cruise conditions. The en route noises were ground-level recordings of eight advanced turboprop aircraft flyovers and six conventional turbofan flyovers. The eight advanced turboprop en route noises represented the NASA Propfan Test Assessment aircraft operating at different combinations of altitude, aircraft Mach number, and propeller tip speed. The conventional turbofan en route noises represented six different commercial airliners. The overall durations of the en route noises varied from approximately 40 to 160 sec. In the experiment, 32 subjects judged the annoyance of the en route noises as well as recordings of both the takeoff and landing noises of each of 5 conventional turboprop and 5 conventional turbofan aircraft. Each of the noises was presented at three sound pressure levels to the subjects in an anechoic listening room. Analyses of the judgments found small differences in annoyance between three combinations of aircraft type and operation. Current tone and duration corrections did not significantly improve en route noise annoyance prediction. The optimum duration-correction magnitude for en route noise was approximately 1 dB per doubling of effective duration. Introduction Concerns about the impact of aircraft noise on people have traditionally centered around the takeoff and landing operations of aircraft in the vicinity of airport terminals. The development of advanced turboprop (propfan) propulsion systems, modifications to air corridors, and the desire to maintain a natural environment in national parks and recreation areas have now focused attention on the impact at ground level of the en route noise produced EPNL by aircraft at cruise conditions and altitudes (ref. 1). LA Compared with terminal-area noise (i.e., takeoff and landing noise), cn route noise is characterized by rclLD atively low noise levels, a lack of high-frequency specLL z tral content, and long durations. Much research has been directed towards understanding and quantifying PL the annoyance caused by terminal-area aircraft noise, but relatively little research has been conducted for PNL en route noise. procedures and corrections to predict annoyance to en route noise; and (4) to determine whether modifications to the duration-correction method wouhi improve the prediction of annoyance to en route noise. Noise Metrics, Symbols, and Abbreviations Noise Metrics effective perceived noise level, dB A-weighted sound pressure level, dB D-weighted sound pressure level, dB Zwicker loudness level, dB perceived level (Stevens Mark VII procedure), dB perceived noise level, dB To address this need, a laboratory experiment was conducted to quantify the annoyance response of people on the ground to en route noise generated by aircraft at cruise conditions. The specific objectives were: (1) to compare the annoyance responses to en route noise with the annoyance responses to takeoff and landing noise; (2) to compare the annoyance responses to en route noise of advanced turboprop aircraft with the annoyance responses to en route noise of conventional turbofan aircraft; (3) to determine the ability of current aircraft noise measurement Detailed descriptions of the noise metrics used in this report can be found in references 2 and 3. Symbols and Abbreviations ATP advanced turboprop a0, al, a2 constant coefficients D* duration correction based on a nonoptimum duration-correction magnitude expressed in terms of decibels per doubling of effective duration, dB