Computer-steered microphone arrays for sound transduction in large rooms

The quality of sound pickup in large rooms—such as auditoria, conference rooms, or classrooms—is impaired by reverberation and interfering noise sources. These degradations can be minimized by a transducer system that discriminates against sound arrivals from all directions except for that of the desired source. A two-dimensional array of microphones can be electronically beam steered to accomplish this directivity. This report gives the theory, design, and implementation of a microprocessor system for automatically steering a two-dimensional microphone array. The signal-seeking transducer system is implemented as a dual-beam, “track-while-scan” array. It utilizes signal properties to distinguish between desired speech sources and interfering noise. The complete automatic system has been tested in anechoic and medium-sized auditorium environments, and its performance is discussed.