Two procedures for estimating internal noise.

Internal noise was measured in two paradigms simultaneously. In one method the listener's agreement in choosing the same masker as the one in a pair that sounds most signal-like is used to estimate internal noise [D. M. Green, Psych. Rev. 71, 392--407 (1964)]. In the other the increment in detection performance on those trials having identical as opposed to different maskers is used t estimate internal noise [R. A. Siegel, unpublished Master's thesis, M.I.T. (1979)]. Most results place the estimate of additive internal nose as nearly equal to external noise variability. The estimates from the agreement method can be adversely affected by uncertainty regarding the observation interval and interval biases, whereas the estimates obtained with the detection method are highly sensitive to measurement errors.