Virtual reality applications require all kinds of methods to create plausible virtual acoustics environments to enhance the user experience. Here, we present an acoustic paintbrush method that modifies the timbre of a simple room acoustics simulation with the timbre of a measured room response while aiming to preserve the spatial aspects of the simulated room. In other words, the method only applies the measured spectral coloration and alters the simulated and temporal distribution of early reflections as little as possible. Three variations of the acoustic paintbrush method are validated with a listening test. The results indicate that the method works reasonably well. The paintbrushed room acoustic simulations were perceived to become closer to the measured room acoustics than the source simulation. However, the limits of the perceived effect varied depending on the input signal and the simulated and recorded responses. This warrants for further perceptual testing.

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In virtual acoustics, it is common to simulate the early part of a Room Impulse Response using approaches from geometrical acoustics and the late part using Feedback Delay Networks (FDNs). In order to transition from the early to the late part, it is useful to slowly fade-in the FDN response. We propose two methods to control the fade-in, one based on double decays and the other based on modal beating. We use modal analysis to explain the two concepts for incorporating this fade-in behaviour entirely within the IIR structure of a multiple input multiple output FDN. We present design equations, which allow for placing the fade-in time at an arbitrary point within its derived limit.

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