Aiming at the perceptual evaluation of virtual acoustic environments (VAEs), ‘plausibility’ is introduced as a quality criterion that can be of value for many applications of virtual realities. We suggest a definition as well as an experimental operationalization for plausibility, referring to the perceived agreement with the listener’s expectation towards an equivalent real acoustic event. A listening test methodology for the criterion-free assessment of the deviation from this non-explicit, inner reference is proposed. It requires the rating of corresponding real and simulated stimuli in a Yes/No test paradigm, and the analysis of the results according to signal detection theory. The specification of minimum effect hypotheses allows the testing of plausibility with any desired strictness. The approach is demonstrated with the perceptual evaluation of a system for dynamic binaural synthesis in two different development stages.