In this 1992 letter, acoustics expert James D. Chalupník explains to attorney Richard Aramburu how aircraft noise near Seattle's Sea-Tac Airport is measured and rated, focusing on the appropriateness of the Ldn metric and the data used in the FAA's Integrated Noise Model (INM). He outlines the key physical properties of noise—intensity, frequency distribution, and fluctuation over time—and describes how various weighting schemes, particularly the A-weighting (dBA) scale, are used to approximate human perception of loudness and annoyance. The letter also notes the limitations of simpler metrics and introduces more sophisticated rating methods such as Stevens' Loudness Level and Perceived Noise Level for evaluating aircraft noise.Open full document
Notes
March 6, 1992 letter from acoustician James D. Chalupník (Seattle, WA) to attorney Richard Aramburu discussing the appropriateness of the Ldn (Day-Night Level) metric for rating aircraft noise around Sea-Tac Airport and the data inputs to the FAA’s Integrated Noise Model (INM). Covers noise metrics including dBA, A-weighting, B-weighting, C-weighting, Fletcher-Munsen equal loudness curves, Stevens’ Loudness Level (Ll), Perceived Noise Level (PNL/Lpn), decibel logarithmic scale, frequency distribution, sound intensity, and psychoacoustics as applied to SEA-TAC Aircraft Noise Study 2. References Chalupník’s book ‘Evaluating the Noises of Transportation’ (University of Washington Press, 1969).