Handbook for Sound Engineers

762 Chapter 21

21.3.7.8 The Present and Future of Teleconferencing

Most basic teleconference systems are sophisticated
speakerphones with full duplex capability. Mid-level
teleconferencing systems employ automatic micro-
phones mixers and digital hybrids. The most sophisti-
cated systems feature integrated teleconferencing
devices that include multiple inputs with automatic mix-
ing and echo cancellation, mix-minus signal routing
capability, real-time feedback and level control, and
operation via touchscreen.

Personal computers and digital signal processing
(DSP) are becoming the dominant technologies that
drive new developments in teleconferencing.

DSP advances are leading to teleconferencing

systems that provide each participant with a customized

electro-acoustical environment, unique to his or her own

talking and hearing requirements. Advances in back-

ground noise reductions via electronic means are

already impressive, as long as the noise has a repetitive

nature. Microphone arrays that can be steered to best

pick up a talker and steerable loudspeaker arrays are

more prevalent.

But no matter how dominant digital technology

becomes in teleconferencing, the speech input to the

system from the human mouth will be analog, and the

acoustical output to the human ear will also be analog.

And that is the only technology forecast that will be

100% accurate.

Figure 21-35. Schematic of an teleconference system in a board room that uses all loudspeakers in phase and pairs of

microphones in antiphase. Courtesy of Sound Control Technologies, Inc.

CeilingLecternTel. rtn.Monitor

Gain

master

2 Wire/4 wire

switch

Leveler

Leveler

4 Wire receive

4 wire send

To

Record output telco

Acoustic

echo

canceller

N

Lectern

Mute

Monitor

level

Monitor

loudspeaker

Control

+

+

+

+

+









N

Hybrid