A constant-directivity beamforming microphone array
Gary W. Elko, Thomas Clayton Chou, Robert Jack Lustberg, Michael M. Goodwin · The Journal of the Acoustical Society of America · 1994
The quality of audio teleconferencing in large rooms and noisy environments can be increased with the use of steerable directional microphone arrays. A minimum bandwidth of 4 oct is required to faithfully transmit the speech signal. In a typical teleconferencing arrangement, only discrete angular directions are of interest and therefore the microphone steering directions are quantized. A standard delay-sum beamformer can result in noticeable frequency response changes as the talker moves between these steering locations. In an effort to mitigate this problem, a broadband constant-directivity beamformer has been designed and constructed. A few of the algorithms developed in this work will be discussed and compared to existing techniques. Basically, the solution revolves around the design of FIR filters that are inserted in the delay-sum beamformer after each element. A constant-beamwidth 4 oct steerable linear array microphone using directional elements will be described. A real-time implementation utilizing multiple AT&T DSP3210 digital signal processors is also described.