in March 2005
Audio in the Courtroom
By Scott Woolley
With the correct use of technology, everyone involved
will be able to hear and participate.
courtrooms are taking advantage of modern technology
more than ever before.
Each year, the Chief
Justice of the United States Supreme Court issues a year-end
report on the federal court system. The 2004 report addresses
the funding crisis currently affecting the federal courts
and states that the strategy to reduce costs includes promoting
more effective use of technology. This focus on technology
extends to the state and local courts as well, and directly
relates to the effective use of audio systems in courtrooms.
The audio system is arguably
the most fundamental and important technology in a courtroom.
If the proceedings cannot be heard clearly by all parties,
there is really no benefit to using other technologies such
as videoconferencing or video evidence presentation. In
addition to meeting the functional requirements, which are
discussed here, the audio system must provide cost savings
to court operations by incorporating features such as audio
conferencing, which can reduce the cost of transporting
prisoners between the jail and the courthouse by enabling
remote arraignments. It must also have a low cost of installation,
operation and maintenance.
Implementing a System
Implementing such a system
can be achieved by using digital audio equipment that features
automatic mixing, routing, audio processing and echo cancellation.
Using a single product that performs all of these key functions
simplifies installation and makes it easier to integrate
important features, including assistive listening, audio
recording, sound reinforcement and conferencing. Because
non-technical users, such as judges, clerks and others,
are often required to operate the audio system, an intuitive
user interface is essential for seamless operation [see
Diagram 1. Courtroom
Audio Installation Using a single product to perform
essential audio functions such as automatic mixing,
routing, audio processing and echo cancellation
makes it easier to integrate other elements of the
audio system, including conferencing, recording
and assistive listening.
Close attention should also
be given to infrastructure requirements, such as wiring,
equipment location, and necessary space for existing and
future equipment. Besides the technical issues, the architectural
nature of courtrooms raises aesthetic concerns because interior
design elements of courtrooms often conflict with the acoustic
requirements for providing a high level of intelligibility.
Audio System Requirements
The functional requirements
of a courtroom audio system include providing local sound
reinforcement, assistive listening capabilities for the
hearing impaired, support for translation services, recording
of court proceedings, audio teleconferencing, audio for
videoconferencing, playback of evidence, media feeds and
remote audio monitoring in chambers, clerk’s offices
and the offices of those responsible for court security.
For privacy reasons, infrared
(IR) assistive listening systems are typically used. Because
the IR signal does not penetrate the courtroom walls, it
cannot be picked up by a radio receiver outside the courtroom.
This same IR system is used often for language translation
because the translation system has to be able to support
a translator located in the courtroom or a translator who
is accessed by a telephone line.
Multi-track audio recorders
are used to create a record of proceedings. By routing the
audio from each microphone in the courtroom to a different
audio track, it is easier to identify who is talking on
the recording. Some courts use analog tape recorders to
accomplish this, but most are moving to digital recorders.
Be sure to determine the input level for the recorder because
some require a mic-level signal and others a line-level
signal. Consider providing both types to ensure present
and future compatibility with the court’s audio recording
It is important that the court
reporter making a transcript of the proceedings be able
to easily hear all that is being said. This means that the
reporter may need to be able to adjust levels for individual
microphones, a loudspeaker or for headphones at his or her
location without affecting the primary loudspeakers in the
courtroom. This requires that the system allow for different
signal mixes for multiple outputs.
Typically, it is best to provide
a mix-minus, zoned speaker system. A mix-minus system provides
a mix of all microphone signals at a local loudspeaker,
minus a signal from the local microphone(s). This keeps
microphone signals from being routed to loudspeakers that
are close by and decreases the likelihood of feedback.
Users Have Little Experience
Many of the individuals involved
with court proceedings have little or no experience using
microphones. Some may speak loudly and others softly. This
is especially true of witnesses. Due to the variances in
talking levels and the likelihood that witnesses will not
always speak directly into the microphone, it is beneficial
to use automatic gain control (AGC) on the witness microphone.
AGC is used to ensure consistent voice levels by automatically
increasing gain when the level is too low and decreasing
gain when it is too high.
It is also beneficial to use
AGC on other microphones, such as the counsel table microphones
and the lectern microphone. In addition, AGC can be used
on line inputs that experience fluctuations in audio level.
These audio level fluctuations are common on videotapes,
surveillance audio recordings and wire tap recordings, for
Audio conferencing is something
courts are depending on more and more to help lower costs.
It is used when participants do not have to be present in
the courtroom, such as preliminary hearings, judge conferences
and remote witnesses. The audio conferencing system is an
integral part of the total audio system. It uses the microphones
in the courtroom to pick up the audio and send it to the
remote location, and it uses the courtroom’s loudspeakers
to produce the audio signal from the remote location.
A key to achieving high-quality
audio conferencing is a close marriage of the sound system’s
automatic mixer and the audio conferencing system’s
acoustic echo cancellers (AEC), which prevent echo during
an audio conference. Performing the functions of the AEC
and automatic mixer in the same digital signal processor
reduces the pickup of reverberation and noise from the microphones,
which increases audio intelligibility.
By implementing mixing functions
completely in the digital domain in conjunction with the
AEC, precision in making auto mixing decisions greatly increases.
For example, when audio from another source, such as conference
audio from another room, is amplified through the speakers
in the room, an automatic mixer typically would activate
at least one microphone, as if that audio were coming from
a voice in the room. This false activation can be prevented
by using an automatic mixer that takes the same audio sample
from the AEC process to determine that this audio is coming
from the loudspeaker and not a talker in the local room
(see Diagram 2).
Diagram 2. False
Microphone Activation Audio from a distant room
is sampled before exiting the loudspeaker. The automatic
mixer identifies this audio sample as that coming
fromt he loudspeaker and not a talker in the local
room to eliminate false activation of microphones.
In a courtroom, microphones
are placed in front of judges, clerks, witnesses and attorneys.
Each location has its own unique requirements that must
be considered when selecting microphones.
The manner in which the attorneys
may speak varies depending on the preference of the court.
Sometimes attorneys address the judge or others in the courtroom
while seated and other times they are required to stand.
This makes selection of the proper microphone at the counsel
table important. Typically, a gooseneck microphone with
a directional pick-up pattern is best. The neck of the microphone
has to be long to allow for the base to be positioned at
the back of the table to provide plenty of room for papers
and other materials. A long gooseneck also allows the microphone
to be adjusted easily to be closer to the mouth of the speaker,
regardless of whether that individual is sitting or standing.
During jury trials, there
are times when the judge has to speak privately with the
attorneys in the courtroom. To increase the privacy of the
conversation, masking noise is activated via the loudspeaker
system in the area of the jury. This noise keeps the jury
from understanding the discussion between the judge and
the attorneys. The judge’s microphone also has to
be muted to keep the conversation from being overheard.
However, this conversation
still has to be recorded as part of the official transcript
of the trial, so a special “bench conference”
microphone should be used at the judge’s bench to
pick up the audio from these conversations. The signal from
this microphone is routed to the recording system and also
to the location where the court reporter sits. The court
reporter can listen to the conversation with a set of headphones
and document the conversation.
Diagram 3. AV Equipment Placement
Placement of AV equipment, concentrating here on
microphone and speaker requirements, in a typical
System electronics should
be located in a convenient space outside the courtroom,
with adequate ventilation and plenty of room to access and
service the equipment. Placing equipment inside the courtroom
often limits future growth. In many poorly designed courtrooms,
the equipment is placed under the clerk’s desk or
the judge’s bench, which results in cramped and uncomfortable
spaces for these individuals. It also makes it impossible
to maintain or adjust the system without disruption of court
A network connection should
be provided to the equipment room to allow for remote setup,
monitoring and configuration of the system. An analog phone
line for audio conferencing is also required. Although it’s
true that many phone systems are moving to VoIP, it’s
still wise to plan for the use of a plain old analog phone
The most flexible means of
handling wiring is to use a raised floor system, which provides
maximum flexibility for future growth and allows for reconfigu-ration
of the courtroom’s well area to best serve the needs
of the court. A raised floor system typically has a higher
upfront cost than when using standard conduit, but it can
provide cost savings over the life of the courtroom. This
savings comes when changes to the courtroom require installation
of additional conduit and floor boxes. These types of modifications
and the time that the courtroom is unusable during construction
can become a substantial cost to the court.
placed under the clerk's desk results in a cramped
and uncomfortable space.
If an existing courtroom
is being upgraded and the nature of the existing construction
does not allow for implementation of a raised floor system,
then the size of conduits should be calculated carefully
to ensure plenty of spare capacity, and floor boxes should
be oversized to provide for future growth. If a video evidence
system is not being installed with the audio system, the
conduit/raceway system should be sized to allow the installation
of these systems at a future date. Wire raceways have to
allow for installation of the system cabling in a home-run
fashion, not daisy chained from electrical box to electrical
Many courtrooms are ornate,
with high ceilings and substantial mill- and stonework.
Often, in older, historic courtrooms, architectural features
cannot be modified. As a result, items such as visible wires
are not acceptable. This requires creativity in integrating
the sound system. For example, distributed ceiling-mounted
speakers typically are used in courtrooms, but if a courtroom
has an ornate ceiling or a ceiling that is not accessible
for wiring, beam-steering loudspeakers with a tight vertical
pattern can be mounted at the front of the courtroom. It
is important to perform the calculations required to determine
if the proposed speaker system will provide a high level
The hard surfaces and the
high ceilings in courtrooms often cause significant reverberation.
Without taking actions to reduce the reverberation, it can
be difficult to design a speaker system that will provide
intelligible sound and acceptable audio quality. Reverberation
can be controlled or minimized through acoustic room treatments
such as installing acoustic panels, hanging curtains on
the windows and adding carpet.
Wire raceways are required
in counsel tables to conceal microphone and other system
cables. When wire ways at the judge’s bench, clerk’s
desk and witness stand are installed, they should be concealed
completely. Before ordering, colors for all visible equipment
such as connection panels must be approved by the court’s
The audio system should be
self-operating, with little intervention required by court
personnel. Because it usually is controlled remotely by
the judge from the bench or the clerk from his or her desk,
the control interface must be simple to use, with a limited,
straightforward set of functions. Controls may include power
on/off, bench conference, mute/un-mute and dialing functions
for audio teleconferencing. Level control typically is not
needed, except for auxiliary inputs. Due to the limited
functions of the user controls, it is often possible to
have a button panel control system that connects directly
to the audio system’s digital mixer.
High, ornate ceilings
or ceilings without wire access require creative speaker
placement, such as at the front of the courtroom or
in the floor of the jury box.
||The microphones at the counsel table should be long
enough to allow for the base to be positioned at the
back of the table to provide plenty of room for papers
and other materials, and to be easily positioined closed
to the mouth oi the attorney when sitting or standing.
By careful needs assessment,
planning of infrastructure requirements and the use of modern
digital audio equipment, audio quality in courtrooms can
be improved and the cost of integration can be reduced.
By including functions such as audio conferencing within
the audio system, courtroom operating cost can be reduced
Scott Woolley heads up ClearOne
Communications’ product training and has more than
20 years of experience in audio engineering and systems
consulting and integration. This topic stems from his experience
as a systems integrator, and working directly with systems
integrators on courtroom projects.