Acoustical measurements and prediction of psychoacoustic metrics with spatial variation

The use of sound pressure levels is not adequate to assess and predict environmental sound quality at different locations. Moreover, there is a lack of studies investigating the psychoacoustic metrics with spatial variation. This study aims to investigate (1) the effects of spatial factors (distance and sound emission orientation) on three physical acoustic metrics (root-mean-square sound pressure (P_rms), unweighted sound pressure level (L_Z), and A-weighted sound pressure level (L_A)) and two psychoacoustic metrics (total loudness (N) and sharpness (S)); and (2) the role of the metrics and their statistical parameters in characterizing acoustical properties, through measurements of steady directional high-frequency sound at different points in an anechoic chamber. The results indicate that the sound intensity metrics L_Z or L_A as well as the subjective loudness metric N are distance-dependent. The value of N was approximately equal to 0.727 times the original loudness when doubling the distance from the source. Strong correlations were found between four sound energy content-related metrics (P_rms, L_Z, L_A, and N). However, the fifth metric (S) was closely related to sound spectral content. Moreover, the interquartile range of N was found to be an option of representing sound temporal content. This is the first study to establish the predictability of psychoacoustic metrics with spatial variation. These findings provide a new insight into environmental sound quality assessment and prediction.