Appendix 355

Simulating Reverberation Enhancement Systems Using the CATT-Acoustic Program

Svensson, P. Dept. of Applied Acoustics, Chalmers University of Technology, S-41296 Gothenburg, Sweden.

Computer simulation of electroacoustic reverberation enhancement systems (RES) for auditoria proceeds in two stages. First, the room impulse responses (from the source and all loudspeakers to the receiver and all microphones) are predicted as described in a companion paper by Dalenb/ick. The electronic units are specified by their impulse responses. Secondly, the impulse responses are convolved and added yielding the total room impulse response of the hall with the RES installed. Various objective criteria can be calculated both for the total room impulse reponse and for the room impulse response of the RES alone. A typical medium sized hall seating about 450 persons has been modelled. In this hall three different RES configurations have been simulated, all using two loudspeakers and two microphones. For each configuration three different reverberation units have been simulated. More complex systems can be studied than was possible with previous methods since transducer directivities and individual channel reverberation can be included. It is shown that these parameters, along with the system delay, to a large extent influence the early part of the total impulse response. The risk of instability for complex systems can thus also be studied.

To be published as: Influence of electroacoustic parameters on the performance of reverberation enhancement systems. J. Acoust. Soc. Amer.

Auralisation of Reverberation Enhancement Systems

Svensson, P. Dept. of Applied Acoustics, Chalmers University of Technology, S-41296 Gothenburg, Sweden.

Auralisation of electroacoustic reverberation enhancement systems for auditoria is described. The simulation proceeds as described in a companion paper by Svensson, with the addition of auralisation as described by Dalenb/~ck in a companion paper. Sound reproduction can be made either by the use of headphones or through loudspeakers in an anechoic chamber using crosstalk compensation. Thus, the subjective performance of various configurations of reverberation enhancement system can be estimated. Some different system configurations as simulated in a typical medium-sized hall will be studied. Variations are made both in transducer directivities and positions as well as types of electronic reverberation units. For various systems running at the same gain relative to instability, different amounts and types of subjective colouration might be perceived.