This study examines how the spatial characteristics of a sound field affect its loudness. In an experiment, listeners adjusted the gain of stimuli so as to match the loudness of a reference stimulus. The experiment was conducted using binaural stimuli presented over headphones – using stimuli that simulated the sound from eight sound sources evenly distributed in a circle around the listener. Four degrees of diffusivity were tested, ranging from a single active sound source, to all eight sources producing decorrelated sound with identical power spectra. Four power spectra were tested: broadband pink noise, and low-, mid- and high-frequency bandpass-filtered pink noise. The study finds that in modeling the binaural loudness summation of the diffuse stimuli, a binaural gain constant about 1 or 2 dB greater than that of the non-diffuse stimuli provides the least error.
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