Design of a DSP-based 24 bit digital audio equalizer for automotive applications

The project deals with the design and realization of a dedicated board DSP-based for the processing of audio signals for automotive applications (DIGIcar). The I/O interface of the board is composed of two stereo inputs and two stereo outputs. The prototype was realized in a four layer PCB with SMD components. The layers were designed in order to reduce high frequency effects of digital signals on analog audio signals. The DIGIcar board was tested stand-alone with an Audio Precision System 2022. Experiments were performed inside a car too, where the DIGIcar board was interfaced with a four channel power amplifier and connected between audio source and car loudspeakers. A development tool in MATLAB was exploited to synthesize the suitable equalizing filters given standard car acoustic measurements. Then the filters are stored in the board flash EEPROM. A few options are available to tailor the equalizer for different cars. Listening tests and acoustic measurements show the effectiveness and the functionality of the designed board.