The Function of Intensity and Phase in the Binaural Location of Pure Tones. I

Abstract

Logarithmic Law.---The only published quantitative experiments giving the effect of intensity alone are those of Hovda and the author who found a "logarithmic law," viz., that the effect of intensity only was an apparent angular displacement from the median plane proportional to the logarithm of the ratio of intensities at the ears.Logarithmic Law Extended; the Value of the "Constant."---The law just cited is found to be correct for the three frequencies 256, 512, and 1,024 d.v., and for a displacement range from 0\ifmmode^\circ\else\textdegree\fi{} to almost 90\ifmmode^\circ\else\textdegree\fi{}. But some individuals (two out of four) do not have a fused tone or phantom source at the frequency last named and indeed, at other frequencies also. The constant, in the logarithmic law, i.e., the value of the displacement when the logarithm of the ratio of intensities is unity, is ascertained for several individuals at the above frequencies. For each individual the constant decreased with increasing frequency.The experimental method is the one previously used. The logarithmic law is shown not to be an extension of Weber's law, well known to psychologists, but a new law.Computed Values of Intensity Ratios for Given Positions of Source.---The actual intensities obtaining at the ears when a source of sound is placed at different positions relative to the ears are considered and the theoretical results are plotted and compared with the experimental results.Intensity Not an Important Factor.---The wide divergence between experimental and theoretical values shows that an explanation in terms of intensity of the ability to locate a pure tone, 256 to 1024 d.v., is not possible. Intensity cannot be an important factor in localization of pure tones in this range of frequencies.