Abstract
A new method for the estimation of reflection characteristics of a ground and a freefieldspectrum of noise is presented. The method utilizes informations of differencesof ripples created in power and cross spectra of the sound pressure signals that aresimultaneously observed by two microphones closely spaced along an axis normal tothe ground surface. Ground effects will change due to various factors in measuringconditions. Therefore it will be desirable to estimate ground effects simultaneously withthe measurement of sound pressure signals. The proposed method enables one to makean evaluation of ground effects using noise signals themselves even though their frequencycharacteristics are not known. Results of several practical performances in cases of an aircraft fly-over noise and others are also described.
