Handbook for Sound Engineers

1328 Chapter 34

lation of the reflections that would occur in a concert
hall. Microphone usage and placement are similar to
what would be used in the concert hall. An artificial
reverberation device is used through the mixing
console’s effect send and return. The output of the
mixer is fed to a multitap digital delay. The delay taps
are selected carefully and fed to the individual loud-
speaker systems to simulate the reflections that would
be found in a concert hall.
Another approach is to use one or more semicircular
rings of small loudspeakers at increasing radii into the
audience. The rings may be divided into segments. Feed
the rings from the output of the digital delay.
The process is not as straightforward as that of
designing a simple sound reinforcement system and
may take some experimenting. Nevertheless, it can
significantly improve the sound of an outdoor orchestra
and, thus, enhance the enjoyment of the audience.

34.6.4 Artificial Ambience

Large, multipurpose facilities designed for good speech
intelligibility may not be desirable for musical perfor-
mances because they do not have good early reflections
and do not have a well-developed reverberant field.

Some acoustical consultants now design such rooms

with artificial ambience systems designed to add the

early reflections and reverberation that are lacking in

the natural acoustics.

Such systems consist of many microphones and

loudspeakers and very sophisticated amplification,

signal-processing, and control systems. These systems

are complex and expensive but make it possible to hold

a variety of events in a space and optimize the acoustics

for each type of event. The services of a consultant,

experienced in this type of system, are highly

recommended.

34.6.5 Conference and Boardroom Systems

A conference room sound system has special problems

because of the large number of open microphones, their

proximity to loudspeakers, and the frequent added prob-

lems of ambient noise and uncooperative system users.

Some conference rooms are private; that is, they are

designed exclusively for the use of the conferees. Other

conference rooms include facilities for nonparticipating

or infrequently participating observers, such as the

stockholders, the press, or the public. Examples of the

former are the conference rooms of privately held

companies. Examples of the latter are the conference

rooms of publicly held companies, unions, school

boards, and governmental and other organizations. The

sound systems installed in courtrooms are similar to

those in conference rooms that include observers.

The primary difference between the two types of

systems is in the additional loudspeakers (and roving

microphones) needed for the second type of system.

Both systems, of course, often include audio recording

and playback capabilities and may include video play-

back and recording, audio or audio and video confer-

encing capabilities, computer graphics display

capabilities, and so on.

34.6.5.1 Local Sound Reinforcement in a Conference

Room

Microphone choice is important to the success of a con-

ference room system. One school of thought favors

boundry microphones placed on the table in front of

each participant. A boundry mic is inconspicuous and

does a good job of picking up the direct sound from the

talker’s voice. Because the boundry mic element is less

than a millimeter from the table surface, it does not pick

up reflections from the table in the frequency range of

interest. Thus, technically, this is a good choice.

Figure 34-87. Outdoor-rated loudspeakers at a motor race-

track. Courtesy Community Professional.