Binaural Interactions of Impulsive Stimuli and Pure Tones

Abstract

The time-vs-intensity trade ([DELTA]T/[DELTA]I) in binaural lateralization was measured for pure tones and impulsive stimuli by the null method for high-pass and low-pass clicks at a repetition rate of 20 pps and pure tones of 200, 500, and 700 cps. Mean sensation levels (SL) of 20, 30, and 40 db and interaural intensity differences of 0, 4, and 6 db were used. The data on 4 subjects indicate a difference between high-pass and low-pass clicks: for instance, [DELTA]T/[DELTA]l = 0.025 msec./db for low-pass clicks below 1000 cps and I = 30 db, whereas at the same intensity [DELTA]T/[DELTA]l = 0.060 msec./db for high-pass clicks above 4000 cps. It is concluded that the time-vs-intensity trade is important for the localization of high-frequency impulsive stimuli. The interaural intensity difference also affects the ability to lateralize, since the error of lateralization is least when both the interaural intensity difference and interaural time difference are zero. From the foregoing and from experiments with 2 lateralized images, it is concluded that the timing information used in binaural lateralization travels along frequency-dependent neural pathways. Any physiological timing signal must be able to explain this phenomenon.