Inaccurate modeling of scattering remains a weakness of room acoustics auralization. How well must scattering be modeled for accurate auralization? To evaluate the time-frequency perception of scattering in the binaural room impulse response, one can begin by investigating the audibility of Frequency-dependent changes in Lambert diffuse reflection. Listening tests are performed to compare computed auralizations of a Swedish concert hall. In this study one finds the following: (1) For some signals, changes in the diffusion coefficient are clearly audible within a wide frequency region. Thus, diffuse reflection should be modeled in a frequency-dependent manner, although not all auralization programs currently do this. (2) The perception of these changes depends on the input signal. For sustained signals (e.g., an organ chord, pink noise), changes are strongly perceived as differences in coloration; for example, increasing low-frequency diffusion is perceived as "decreasing the bass" content or "increasing the treble" content of the signal. For impulsive signals (e.g., string pizzicato), coloration differences are less audible than for sustained signals, whereas spaciousness differences are relatively stronger. It is interesting that listeners, though uninformed of the differences between high- or low-diffusion signals, give consistent answers regarding perceived changes in frequency coloration. [References: 15]
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