Specifications

Appendix B
Shure microphones and automatic mixers have emerged
as the product of choice for courtrooms, video arraignment
chambers, and other legal facilities. The following are helpful
hints on designing and implementing a successful audio
system using Shure products.
Suggested Microphones and their Placement
• A low profile surface mount microphone is often chosen for a courtroom
because of its styling. However, this type of microphone should not be placed
near any vertical surface that could cause acoustic reflections into the rear
of the microphone. This can be difficult to achieve at a lawyer’s tables or the
judge’s bench. For example at the judge’s bench, a nameplate or a vertical
privacy panel may reflect the talker’s voice and cause inconsistent gating or
degradation of the microphone’s acoustic performance.
• If a low profile surface mount microphone is used at the judge’s bench, it
should be positioned so that the rear of the microphone is not blocked in
any way. Often a small wooden block can be placed under the microphone
to raise it higher than a privacy panel. Or the privacy panel can be covered
by sound absorbing material (1” or 2” fiberglass covered in porous cloth)
to reduce the acoustic reflections.
• Note that because of the low profile microphone’s inconspicuous
appearance, it is common to have court documents or briefcases
accidentally covering the microphone. This will result in very poor audio.
• In place of the low profile surface mount microphone, consider using either
a gooseneck mic or the stand mounted mic As these mics are placed
above the table or bench surface, paper shuffling or table tapping noise will
not be as troublesome.
Judge Position
• A privacy switch is normally required for sidebars. Always use the
automatic mixer’s MUTE logic terminals to provide this feature. Note that
with the Shure AMS automatic mixer, the Off-Attenuation control sets the
“depth” of the muting provided when the MUTE terminal is used.
• A visual indicator, like a light emitting diode (LED), showing if the judge’s
microphone is muted or active is commonly installed where the judge can
easily see it. This indicator is controlled by the automatic mixer’s GATE
OUT terminal.
• An all-mute switch can provide the judge manual control over every
microphone in the system. The automatic mixer’s MUTE terminals are
employed for this feature.
Court Clerk Position
• The clerk’s position should include a switch to mute or activate the
microphone for the jury foreman. This switch is normally single pole/double
throw (SPDT) and is wired to alternately ground the automatic mixer’s
MUTE terminal or OVERRIDE terminal. This configuration gives complete
manual control of the jury microphone to the City Clerk. This switch could
also be mounted at the judge’s position.
• A control panel connected to the automatic mixer’s logic terminals can be
located at the court clerk’s position. MUTE and OVERRIDE for each
individual microphone are typical controls or an all-mute switch would give
the clerk control over every microphone in the system.
• Some clerks are also responsible for video recording of courtroom
proceedings. For automatic camera selection, the automatic mixer’s GATE
OUT terminals can be used to control the Shure AMS880 video switcher
interface. The AMS880 will direct a video switcher to call up a certain
video camera based on which microphone is activated.
Attorney’s Position
• Standard features are a privacy switch using the automatic mixer’s
MUTE terminal and an illuminated visual indication if the microphone is
muted or active.
• A gooseneck microphone or stand mounted microphone is recommended.
As the microphone is positioned above the table surface, noise from paper
shuffling or table tapping is less likely to activate the microphone or be
heard through the sound system. A low profile surface mount microphone
will always pick up a great deal of unwanted paper noise because the
microphone is on the table surface.
• A custom-made rigid tube is an attractive way of mounting a microphone. This
eliminates the possibility of an attorney repositioning the microphone incorrectly.
• If a low profile surface mount microphone must be employed, make certain
that the rear of the microphone (where the cable exits) is not facing any
surface that may reflect sound, like a nameplate, briefcase, or a privacy
panel. The reflective surface may interfere with the automatic activation of
the microphone or may degrade the acoustic performance of the
microphone. [A low profile surface mount microphone may be placed on
top of a privacy panel.] If it is absolutely necessary to position a low profile
microphone close to a reflective vertical surface, a sound absorbent panel
(1” or 2” thick fiberglass covered with open weave fabric) should be
installed so that the surface is made as absorptive as possible. This can
often improve the inconsistent activation that will may occur if the reflective
surface is not treated. Remember, most low profile surface mount
microphones are designed to work properly only when the rear of the
microphone is facing an open space.
P.A. Feed
• The outputs of the automatic mixer can feed a number of separate devices.
The main output generally feeds an equalizer and power amplifier to
provide the sound reinforcement needs of the courtroom. If there is an
Auxiliary output, it generally feeds a dedicated tape machine which records
the court proceedings.
• The automatic mixer’s logic terminals are often used to control loudspeaker
muting relays for distributed loudspeaker systems. Commercially available duck-
ers and TTL logic-to-relay converters also are useful for loudspeaker muting.
• In very large courtroom, a “mix-minus” matrix design may be appropriate.
In this type of system, a group of microphone signals are fed to all
loudspeakers except the loudspeakers closest to the microphones’
location. This helps improve control over acoustic feedback.
Recording Applications
• A multi-track tape machine is often used to record the proceedings.
One track is often dedicated to document the entire hearing for the public
record. The remaining tracks are used to individually record the judge,
witness, and attorneys.
• If it is necessary to record more than one microphone on a single track, the
Direct Outputs from the automatic mixer can be paralleled to feed that
track. Normally, up to twelve Direct Outputs can be connected together.
• A “default”microphone is often employed to maintain a suitable amount of
courtroom ambient sound in the recording. This microphone is activated
only if all other microphones are inactive.
Broadcast/Press Feeds
• A distribution amplifier is a useful device to provide multiple separate feeds
from the automatic mixer. Each output of a typical distribution amplifier is
switchable for mic or line level providing broadcasters the feed level of their
choice. As a distribution amplifier's outputs are isolated from each other,
a shorted cable plugged into one output will not affect the other feeds.
• As in Recording Applications, a default microphone should be used to
maintain courtroom ambient sound to the broadcast feeds.
38
MEETING FACILITIES
Audio Systems Guide for
Appendix B:
Design hints for courtrooms
and video arraignment chambers
Reference Information