EVALUATION OF THE NOISE FIELD AROUND JET-POWERED AIRCRAFT

Analysis of the effects of noise on the activities of human beings is usually difficult and uncertain. Recently developed means of evaluating these effects are reviewed. The analysis hinges on the use of the “Speech Interference Level”, a nearly non-subjective criterion which is particularly useful. Calculations based on measurements of noise levels near a J-47 turbojet engine, and on recently collected data for sound attenuation in the atmosphere are used as examples. Data are presented in a novel form utilizing overlays to show the ground intersection of equal speech interference surfaces when a hypothetical airplane is flying at specified altitudes. With a map of appropriate scale, the overlays may be used to study the effect of such flights on any ground area. The data are also presented in the form of hemispherical domes or igloos of specified Speech Interference Level around a point on the ground. Assumptions are described and discussed.