Audio effects for multi-source auralisations

Implementing multi-source auralisations is essential for comprehensive acoustic studies of concert halls, operas, restaurants and other spaces, where many sound sources are active. Nowadays, room simulation programs and computers are fast enough to calculate the many impulse responses required for such auralisations, in short time. However, setting up the calculations for the entire ensemble of sources and corresponding signals requires a lot of time-consuming manual work and a large number of recorded source signals. To facilitate the process of creating multiple source signals, with sufficient variation for auralisation, a set of audio effects has been developed in the ODEON Room Acoustics Software [1]. The effects can be combined together and help to create a population of incoherent output signals by varying certain attributes of just a single input signal. Two examples are: a) A group of violins, composed of several signals that have been generated as variations of just one violin recording, using individually randomized Chorus, Spectrum and amplitude effects. b) A number of speech signals with a given output length, created by performing randomized pitch change, tempo shift and random amplitude modulation. The length of the output speech signal can be obtained by time shifting and repeating each of the processed signals with pauses of random length in-between until the desired total length is obtained.