A robust asymmetry in loudness between rising- and falling-intensity tones.

Tones rising in intensity over a few seconds are perceived as louder than symmetrical tones falling in intensity. However, the causes for such perceptual asymmetry, as well as its magnitude and dependency on contextual and methodological factors remain unclear. In this paper, two psychophysical experiments were conducted to measure the magnitude of this asymmetry for 2-s, 15-dB intensity-varying tones in different conditions. In the first experiment, participants assessed the global loudness of rising- and falling-intensity sounds with an absolute magnitude estimation procedure (AME); in the second experiment, they compared sounds relatively in an adaptive, two-interval, two-alternative forced-choice task (2I-2AFC). In both experiments, the region of intensity change, the design of experimental blocks, and the type of comparison stimulus were systematically manipulated to test for contextual and methodological factors. Remarkably, the asymmetry was virtually unaffected by the different contexts of presentation and similar results with 2I-2AFC and AME measurements were obtained. In addition, the size of the effect was comparable over all but the highest intensity regions (80-90 dB SPL), at which it was significantly smaller. All together, these results indicate that the loudness asymmetry is preserved under different measurement methods and contexts, and suggest that the underlying mechanism is strong and robust. In short, falling tones have to be about 4 dB higher in level than symmetrically rising tones in order to be perceived with the same global loudness, a finding that is still not predicted by current loudness models.