Loudness adaptation: fact or artifact?

In the present study, the authors tested the hypothesis that contrast effects confound the Ipsilateral Comparison Paradigm (ICP). Bidirectional referents were used in which base tones of 50 or 70 dB alternated with referents of greater or lesser intensity in a 3.5-min listening period. The contrast hypothesis leads to the expectation that the bidirectional referents would produce opposing effects that should nullify time-based loudness changes in the common base tone. Contrary to that expectation, base-tone loudness declined significantly over time in the context of the bidirectional referents, and the loudness of the referents also declined significantly over time. Thus, the results of the study testified to the validity of the ICP as a contrast-free measure of broad-based loudness adaptation.