Lateralization threshold of a signal in noise.

Experiments are described in which the accuracy of the perceived lateral position of a signal against a continuous background of masking noise is determined. Both signal and masker consisted of octave bands of thermal noise, with the same center frequency of 500 Hz. The signal‐to‐noise ratio and signal duration served as parameters. The results can be understood on a statistical basis, the random fluctuations of nerve impulses playing an important role. The fluctuations due to “internal” noise are found to have a standard deviation of about 80 μsec. It appeared that, as a result of the increase of the sound‐pressure level, the onset part of the signal contributes more to the lateral position perceived than the ongoing part does. The relation to the precedence effect is discussed. The statistical procedure underlying the accuracy of the lateral position perceived suggests an approach to the binaural masking level difference effect based on a masking pattern in the binaural‐hearing mechanism.