Loudness evaluation of urban soundscapes by a cross-modal matching method

Abstract

In a previous study, loudness of a time-varying pure tone was evaluated using a cross-modal matching method. In this procedure, the loudness was matched to an equivalent muscular force. Subjects had to judge the instantaneous and global loudness using a proprioceptive input device with force feedback. Using this technique, subjects could respond easily, rapidly, continuously, and with feedback concerning their evaluation. The present study examines the relation between instantaneous and global loudness of 16 urban soundscapes lasting about 20 s using the same method. First, the procedure is individually calibrated with 1-s soundscapes presented at different sound-pressure levels. The data obtained for each subject fit well with a linear relation on a log–log scale between the sound-pressure level in dB and the associated force in log Newtons. Then, the global judgments are performed under two experimental conditions: one with instantaneous loudness evaluation during stimulus presentation and one without. Good correlation was found between these two judgments. The global judgment and the average over the instantaneous matching contour are nearly identical. In addition, a fluction factor (FI) calculated on the loudness judgment contour reflects the degree of movement produced by the subject as well as the presence of discriminable sources.