Tone-on-tone binaural masking with an antiphasic masker

One pure tone (500 Hz) was used to mask another pure tone of the same frequency and duration. The signal and masker were presented in three binaural stimulus configurations, Mo-So, Mo-Sπ, and Mπ -So. The Mo-So condition is a diotic condition; the Mo-Sβ condition is a dichotic condition in which the masker is homophasic and the signal is antiphasic; and the Mπ-So condition is a dichotic condition in which the masker is antiphasic and the signal homophasic. The signal-to-masker ratio required for detection was measured in each condition as a function of the signal-plus-masker phase angle, α. The data showed that the difference in detection between the Mo-Sπ and Mπ-So conditions varied between 0 dB when α=0 deg and 11 dB when α=90 deg. The difference in detection between the Mo-Sπ and Mπ-So conditions is due to the Os' sensitivities to the interaural phase difference present in the Mo-Sπ and Mπ-So conditions. The results are similar to those obtained in investigations involving lateralization. The difference between detection in either the Mo-Sπ or Mπ-So condition and that in the Mo-So condition (the MLD) was variable due to differences in the Os' sensitivities in the Mo-So condition.