Appendix C: Designing Audio Conferencing Systems - Polycom SoundStructure C16 Design Manual

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Appendix C: Designing Audio

Conferencing Systems

Reprinted from the BICSI AV Design Reference Manual, the following audio conferencing design material

The goal of audio conferencing is to enable two geographically separated groups of people, referred to as

the local and remote talkers respectively, to communicate as if they are in the same room together with fast

interation and allowing both parties to speak and be heard at the same time.

The following figure shows a typical solution for audio conferencing (or audio for video conferencing) that

consists of local microphones and loudspeakers, an acoustic echo canceller and noise canceller, automatic

microphone mixers, matrix mixers, telephony interfaces, video codecs and possibly some program audio

(such as CD's, DVD's, or video tapes). The rest of this chapter will explore the different aspects of the

following figure in more detail. This type of configuration would be installed in each of the rooms that are

conferenced together.

The challenge in audio conferencing is that the loudspeaker audio is not only heard by the local participants,

but it is also heard by the local microphones and, in the absence of an acoustic echo canceller, will be sent

back to the remote participants causing the remote participants to hear a delayed echo of their voice.

Many of the challenges in audio conferencing arise from microphone selection and placement, loudspeaker

placement, and balancing the architectural and aesthetics of the room with the requirements for having the

best audio quality. Compromises in audio quality in favor of aesthetics will reduce the quality and

intelligibility of meetings.

Polycom, Inc.

Program Audio

Program Audio

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