The assessment of noise, with particular reference to aircraft

Steps leading from the physical assessment of noise to a subjective assessment of its impact on the human population in a given area are discussed in detail. The use of common measuring techniques and their utility as models of the human auditory system are considered. Technical data (oscillograms and results of spectrum analysis) are processed to obtain subjective results. An on-going subjective measure representing the perceived strength of the sound in terms of loudness or noisiness can be obtained from the spectrum data by means of several different algorithms. A subjective characterization of a sound 'event' is then derived from the time history of the subjective measure. Individual events are assembled to provide an index of noise exposure over a period of time, and a summation of the noise exposure index over a given area is carried out to assess the global impact of noise on a population. Progress toward standardization of units, scales, and indices for assessing aircraft noise is discussed.