Hands-free teleconferencing unit using auxiliary loudspeaker and duo-filter echo canceller DSP
Suehiro Shimauchi, Yoichi Haneda, Yutaka Kaneda · The Journal of the Acoustical Society of America · 1999
In many telecommunication systems, hands-free operation is becoming popular. For this to be comfortable and easy, high echo cancellation performance and a simple setup are required. This paper presents a new hands-free teleconferencing unit that consists of a main loudspeaker, an auxiliary loudspeaker, a microphone, and an echo canceller DSP board. The auxiliary loudspeaker is used to reduce the acoustic coupling between the main loudspeaker and the microphone by reproducing the anti-phase sound of the main loudspeaker. Since the auxiliary loudspeaker is set very close to the microphone, its sound level is low enough for users not to hear. Experimental results showed a reduction in acoustic coupling of about 6 dB from 200 Hz to 1 kHz. This unit also incorporates a newly developed acoustic echo canceller (AEC) DSP. The AEC algorithm, which is based on a duo-filter control system [Y. Haneda, S. Makino, J. Kojima, and S. Shimauchi, ‘‘Implementation and Evaluation of an Acoustic Echo Canceller Using Duo-Filter Control System,’’ in Proc. EUSIPCO96 (1996), Vol. 2, pp. 1115–1118], helps to produce good and stable performance even during double-talk.