The Position-Dependent Power Spectrum of Reflected Noise

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Noise appears grossly to shift the power spectrum as a function of distance from the reflecting surface with source and observer static (e.g., the nearer the ear to the reflecting surface, the higher the predominant pitch of the noise appears to be). The predominant pitch similarly appears to be dependent on the angle of reflection (e.g., in contrast to the Doppler effect, the pitch of the noise of an overhead moving source appears to decrease on approaching but appears to increase on passing the observer). Analysis of tape recordings of a ventilating fan noise over a clay floor in a large building demonstrate the variation of the power spectrum as a function of elevation above the clay floor and the angle of reflection.