Signal processing architecture for loudspeaker array directivity control

The work described in this paper concerns development of a specialized signal processing architecture, targeted for LSI implementation, which would make a loudspeaker array with digital directivity control practicable. The solution presented here utilizes a specialized array element signal processor (AESP) to provide the signal processing capabilities required at each loudspeaker array element. Major design issues include distribution of the N bands of digitized audio information to each array element as well as implementation of a tapped delay line at each array element. Here a high speed digital audio bus (HSDAB) is used to distribute all N bands of audio information to each AESP in a time-multiplexed fashion. A "bus catcher" queue (BCQ) at each AESP is then used to capture the bands of interest sent out over the HSDAB; further, the BCQ (implemented as a circular buffer) allows each AESP access to selected "delay taps" at frequency bands of interest. A specialized ALU is utilized by the AESP to perform amplitude equalization and generate a composite output for each driver. A separate, lower speed control parameter bus (CPB) is used to distribute amplitude and phase equalization parameters to each AESP; control parameters as well as the user interface are provided by a system supervisor processor (SSP).