Round‐window potentials evoked by clicks were recorded from anesthetized guinea pigs. By comparingN1amplitudes on line, it was possible to computephysiological difference limensfor click intensity. The method requires no assumptions about the underlying distributions of neural effect. Weber functions were generated with and without a continuous masking noise. The effects of click intensity and of background noise paralleled those previously reported for human listeners. A neural model was described in which variability ofN1amplitude turned out to be the principal parameter.