Towards a yardstick of spatial impression: Psychophysical experiments using virtual piano stimuli

Abstract

A rich “spatial impression” is an important factor in the product value of musical instruments. However, it also represents a development challenge since there is no established method to measure and control it. We introduce a novel yardstick for spatial impression, changing tacit knowledge into a measurable property. We focused on the difference in spatial impression between digital pianos and grand pianos, and conducted psychophysical experiments using piano sounds to identify the features that contribute to grand pianos’ spatial impression. We used multiple virtual stimuli which are created by varying physical parameters and conducted the experiment in a virtual environment including head-tracking from a VR headset. This allowed us to find a trend in the spatial impression and identify a physical parameter that correlates to the perceptual results of the experiment. This parameter, “phase entropy,” denotes the time complexity of the interaural phase difference. The correlation coefficient between the psychophysical experiment results based on virtual stimuli and the phase entropy was 0.8752. In addition to the virtual stimuli, we confirmed the correlation between perceptual score and phase entropy in an experiment using actual piano recordings; the correlation coefficient in this case was 0.6500.