DAFX: Digital Audio Effects, Second Edition

5.7 Modeling of Room Acoustics

The room effect, i.e., the room impulse response, can be created by modeling how sound propagates and reflects from surfaces if the geometry of a room is available. Such a process is called room acoustics modeling and several techniques are discussed in Section 5.7.4. In many cases the geometry of a room is not needed since an artificial room impulse response can be created from a perceptual point of view. In fact, the human hearing is not very sensitive to details in the reverberant tail and any decaying response can be used as an effect.

Even if we have enough computer power to compute convolutions by long impulse responses in real time, there are still reasons to prefer reverberation algorithms based on feedback delay networks in many practical contexts. The reasons are similar to those that make a CAD description of a scene preferable to a still picture whenever several views have to be extracted or the environment has to be modified interactively. In fact, it is not easy to modify a room impulse response to reflect some of the room attributes, e.g., its high-frequency absorption. If the impulse response is coming from a room acoustics modeling algorithm, these manipulations can be operated at the level of room description, and the coefficients of the room impulse response are transmitted to the real-time convolver. In low-latency block-based implementations, we can even have faster update rates for the smaller early chunks of the impulse response, ...