Effect of dichotic presentation on the recognition of telegraphy signs

The recognition of telegraphy signs (Morse code) masked by noise was studied at different interaural phase conditions at 250, 500, 1000 and 2000 Hz tone frequency in eight normal-hearing men. The possible effect of a left-right ear of dominance was considered. Best recognition was obtained at 500 Hz tone frequency with the telegraphy signs 180 degrees out of phase but with the noise in phase. When the telegraphy signs and noise were presented in one ear, recognition improved when the same masking noise without any phase difference was added to the other ear. The effect was most marked at 500 Hz. No significant difference was found between the left and right ear.