THE INFLUENCE OF ONSET SOUND LEVEL OF TEST STIMULUS ON REPORTED MAGNITUDE OF CHANGING-LOUDNESS AFTEREFFECTS

An increasing-loudness aftereffect follows adaptation to a tone of decreasing sound level; a decreasing-loudness aftereffect follows adaptation to a tone of increasing sound level. Contrary to the belief that sensory processing contributes to these changing-loudness aftereffects, evidence suggests that onset sound level of test stimulus may have little influence on reported aftereffects. This was tested formally in the present study. Adapting stimuli and test stimuli all employed 1-kHz sinusoidal carriers:;Three onset sound levels of test stimuli were well within the range of sound levels encompassed by adapting stimuli; a fourth was set at the highest value of this range. Consistent with previous evidence, substantial aftereffects were reported for all the midrange onset sound levels, with little difference across onset sound levels. However, for the high-range onset sound level, reported aftereffects were severely attenuated. Sensory processing can be invoked by supposing that aftereffect mechanisms `'tap'' neural activity that encodes adapting sound levels.