Multi-channel System

Changeability of Room Acoustics

The   Curt-Sachs-Saal of the »Staatliches Institut für Musikforschung« is equipped with a multi-channel PA system. Altogether, 92 loudspeakers are built in the walls and the ceiling, which can transmit 16 channels of music or speech simultaneously. The direction in which the individual channels are projected is partly controlled through the multi-channel Digidesign Pro Tools system. However, the PA system is not only used for conventional sound amplification, but also to design special effects during musical performances.

Another future field of application for the PA system is characterised by the key phrase »changeability of room acoustics«. Suitable equipment shall keep the acoustic properties of a room even if some characteristics of the room change, for example if the reverberation time is shortened. This can by accomplished by either amplifying the diffuse reverberation field (  Multiple-Cannel Reverberation) or the natural resonant frequency (  Assisted Resonance).

Finally, in order to simulate acoustic properties of different rooms in the Curt-Sachs-Hall, all reverberation produced by that hall must be initially filtered from the signal. This is achieved by de-convolving (  Deconvolution) the signal with the impulse response of the Curt-Sachs-Hall. Afterwards, this »dry« sound can be convoluted with an impulse which characterises the desired room acoustics. There is some software available for the convolution of audio signals, but it usually is not efficient enough for multi-channel real time operation.