THE ENVIRONMENTAL NOISE IMPACT OF LIGHT AIRCRAFT: A METHOD FOR COMPARING DIFFERENT LIGHT AIRCRAFT TYPES

This paper describes a method which the RAF Institute of Health in the UK uses to select a 'quiet' light aircraft, as part of a procurement procedure. A rank-ordered marking scheme was designed to assess the relative loudness-nuisance level of each aircraft for four parameters: (1) aircraft noise level; (2) the SPL of the blade passing frequency; (3) the frequency spectrum of the noise; and (4) subjective value of eleven 'common' flight conditions. Two video tracking cameras recorded aircraft height and lateral offset of flight path, to ensure valid noise measurements. Lamax, Laeq, Lae, and associated 1/3 octave band frequency spectra noise indices were recorded during the trial; they were used to estimate the annoyance and nuisance parameters of each aircraft, by evaluating and comparing the assessment parameters. For each of six types of aircraft, tables give the noise level data, specification of aircraft type, and individual and overall assessments. The blade passing frequency is the most obvious, and using the most annoying element of aircraft noise. The method described here was shown to be a good way of grading aircraft type, but it is essential to use the same operating and measurement methodology for each aircraft type being considered. For the covering abstract, see IRRD E100715.