Digital Sound Field Control System for Car Audio

The flexible hardware for a digital sound field control has been developed. This is used to develop an audio system which controls sound fields in vehicles. Two kinds of input signal can be selected. They are the digital output of a CD player and the analog output signals of tuner, tape deck, etc. This hardware has two DSPs (Digital Signal Processor) for fast calculations and an external 64k word RAM for delay data of stereo signals. This hardware is controlled by the host computer transmitting several parameters. This hardware can generate fifty-five early reflected sounds, maximum delay time of which is 700msec in a sample time interval of (= 1/44.1kHz = 22.7μsec). The output signals processed by the DSPs are connected to any 6 channel digital to analog converters. The sound field can be changed on real time by transmitting the early reflected sound parameters made in a file of the host computer through the serial interface. By using this hardware, 9 band stereo graphic equalizing and 4 channel convolution of reflections are realized.