A comparison of methods for investigating the perceptual center of musical sounds

In speech and music, the acoustic and perceptual onset(s) of a sound are usually not congruent with its perceived temporal location. Rather, these "P-centers" are heard some milliseconds after the acoustic onset, and a variety of techniques have been used in speech and music research to find them. Here we report on a comparative study that uses various forms of the method of adjustment (aligning a click or filtered noise in-phase or anti-phase to a repeated target sound), as well as tapping in synchrony with a repeated target sound. The advantages and disadvantages of each method and probe type are discussed, and then all methods are tested using a set of musical instrument sounds that systematically vary in terms of onset/rise time (fast vs. slow), duration (short vs. long), and center frequency (high vs. low). For each method, the dependent variables were (a) the mean P-center location found for each stimulus type, and (b) the variability of the mean P-center location found for each stimulus type. Interactions between methods and stimulus categories were also assessed. We show that (a) in-phase and anti-phase methods of adjustment produce nearly identical results, (b) tapping vs. click alignment can provide different yet useful information regarding P-center locations, (c) the method of adjustment is sensitive to different sounds in terms of variability while tapping is not, and (d) using filtered noise as an alignment probe yields consistently earlier probe-onset locations in comparison to using a click as a probe.