Audibility of "diffusion" in room acoustics auralization: An initial investigation

Inaccurate modeling of scattering remains a weakness of room acoustics aura lization. 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 Frequenc y-dependent changes in Lambert diffuse reflection. Listening tests are perf ormed 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 audi ble within a wide frequency region. Thus, diffuse reflection should be mode led 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 sustai ned signals (e.g., an organ chord, pink noise), changes are strongly percei ved as differences in coloration; for example, increasing low-frequency dif fusion is perceived as "decreasing the bass" content or "increasing the tre ble" content of the signal. For impulsive signals (e.g., string pizzicato), coloration differences are less audible than for sustained signals, wherea s spaciousness differences are relatively stronger. It is interesting that listeners, though uninformed of the differences between high- or low-diffus ion signals, give consistent answers regarding perceived changes in frequen cy coloration.