Mechanisms responsible for differences in perceived duration for rising-intensity and falling-intensity sounds

Sounds that are equivalent in all aspects except for their temporal envelope are perceived differently. Sounds with rising temporal envelopes are perceived as louder, longer, and show a greater change in loudness throughout their duration than sounds with falling temporal envelopes. Stecker and Hafter (2000) proposed that participants ignore the decay portion of sounds with falling temporal envelopes to account for observed loudness differences, but there is no empirical evidence support this hypothesis. To test this idea, two duration-matching experiments were performed. One experiment used broadband noise and the other natural stimuli. Different groups of participants were given different instruction sets asking them to (1) simply match the duration or (2) include all aspects of the sounds. Both experiments produced the same result. The first instruction set, which represented participants' natural biases, yielded shorter subjective durations for sounds with falling temporal envelopes than for sounds with rising temporal envelopes. By contrast, asking participants to include all aspects of the sounds significantly reduced the size of the asymmetry in subjective duration, a result that supports Stecker and Hafter's hypothesis. This segregation of the stimulus at the perceptual level is consistent with observed asymmetries in loudness change and overall loudness for sounds with rising and falling temporal envelopes, but it does not account for the entire effect. The remaining portion of the effect, after considering biases due to instructions, is not likely a result of adaptation but could be associated with persistence. The amount of persistence was inferred from behavioral masking data obtained for these sounds.