Potential carry-over effect in the measurement of induced loudness reduction

The majority of studies on induced loudness reduction (ILR) use an experimental paradigm that results in an underestimation of the amount of ILR. Most of those studies utilize loudness matches between tones of two different frequencies (a test tone and a comparison tone) with (experimental condition) and without (baseline condition) an inducer tone at the test frequency. The change in level of the comparison tone between the baseline and experimental conditions is the amount of ILR. In those experiments, the level of the comparison tone in the baseline condition tends to be substantially higher (often about 10 dB) than in the experimental condition. Because of this level difference, exposure to the baseline condition immediately prior to the experimental condition causes unintended ILR for the comparison tone. In this study, the delay between the baseline and experimental conditions was varied and it was determined that the amount of ILR is underestimated by about 30% and the variability is increased when the experimental condition is run immediately after the baseline condition. A second experiment using a Békésy-tracking procedure showed that ILR maximizes rapidly upon exposure to an inducer and decays over the course of several minutes after the inducer is removed.