Loudness in rooms and the sound strength parameter: Linking perception and physical acoustics

Loudness as a perceptual phenomenon has been extensively studied within psychoacoustics. In room acoustics, however, the psychoacoustical factors influencing loudness have yet to be incorporated into standard parameters such as sound strength (G). G is the decibel ratio of the integrated energy of a room impulse response (RIR) compared to the same source located 10m away in a free field. The purpose of this study was to determine how the physical RIR properties measured by G relate to perceived loudness in the same room. Listeners were asked to match pink noise presented anechoically to the perceived loudness of the same noise in a simulated room. Listeners could continuously adjust the level of the anechoic reference. Room simulations were rendered over a 36-channel loudspeaker array in an anechoic chamber. Loudness matches were performed for different room types, source-receiver distances, and source powers, which produced received sound levels between 35 and 85 dBA. Results show a relatively linear relationship between loudness and G. However, it is clear that G underpredicts loudness ratings at higher sound levels. This demonstrates a more complex relationship between G and loudness. Effects of room type and source-receiver distance appear to introduce additional complexity not represented by G.