Comparison of Time Delay and Phase Shift of a Narrow-Band Noise Signal in Binaural Signal Detection

Abstract

The signal employed in most binaural-masking studies is a tone. In the present experiment, signal is Gaussian noise passed through a 50-cps filter centered at 500 cps. The masker is broad-band noise. The signal was shifted in phase by 30° steps between 0° and 180° and delayed by corresponding steps between 0 and 1 msec. The conditions using a noise signal are compared with the same conditions in which a 500-cps tone is the signal. Data were obtained by a 2-interval forced-choice method. The signal levels required for a d′ of 1.5 were determined for all conditions, using a method developed by Jeffress. These signal levels are plotted as masking-level differences (MLD's) relative to the homophasic condition and permit comparison of the various conditions. The functions relating phase shift and time delay of the noise and tonal signals to the size of the MLD are similar in shape. The MLD increases rapidly as the phase shift or time delay increases. Differences in the size of the MLD between corresponding and phase-shift time-delay conditions are small for the noise signal and are approximately equal to the MLD's obtained with a pure tone.