Patent US 4,338,581

Room acoustics simulation is achieved by digitally defining delay and weighting parameters and generating sampled analog signal responses. In the early portion of a response term an accurate impulse response is provided and subsequently high echo density is simulated using sampled analog signal Schroeder sections. A sampled data analog signal device is used which employs charge transfer devices as programmable delay media, multiplying digital to analog converters to generate weighting of the analog signal and a general purpose microprocessor as a parameter calculator. The early impulse response characteristic is accomplished by providing a time domain finite impulse response (FIR) section in a transversal filter arrangement which directly feeds to an ultimate output and to parallel comb filter sections which in turn input to at least one all pass section of the so-called Schroeder configuration. The charge transfer devices are employed as programmable delays to propagate the analog signals. All weighting coefficient products are generated by multiplying digital-to-analog converters.