Use of Noise to Eliminate One Ear from Masking Experiments

To evaluate the possibility that one ear can be eliminated from a masking experiment by use of noise, certain relevant facts were determined. These are: (1) if a tonal signal mixed with noise is received at one ear, the addition of a noise to the other ear slightly reduces the threshold for the tone if the noises are statistically independent; (2) in contrast, the noise added to the nonsignal ear distinctly reduces the threshold for the tone if the noises are perfectly correlated (+1.0); (3) these effects, (1) and (2) above, are observed whether the level of the masking noise at the ear that receives the tonal signal is less than, equal to, or greater than the level of the added noise at the ear that does not receive the tone; (4) if identical tones are presented to the two ears and if the signal-to-noise ratio is about 25 dB lower in one ear than in the other, the effect of the signal at the ear with the lower signal-to-noise ratio is eliminated from the masking experiment.