U.S. Courts Design Guide
The courtroom must not be a long or narrow rectangle finished totally with
sound-reflective materials. Such conditions can cause excessive acoustic fluttering.
Reducing the room length, avoiding the use of long, parallel walls, and using
appropriately selected absorptive finish materials can alleviate the problems.
Noise Reduction
Surfaces. Choice of acoustical treatment depends primarily on the size and shape
of the room. Ceiling treatment, as well as acoustical treatment on selected wall
surfaces, can be necessary. Floors must be carpeted for acoustical control. Walls
must be constructed to prevent sound transmission to and from adjoining spaces.
from mechanical equipment rooms, and must have a large intervening space to
minimize noise transmitted from the HVAC equipment to the courtroom.
Low-velocity air flow with appropriate low-noise diffusers are recommended for
distribution throughout the courtroom. Sound transmission into or out of the
courtroom through the duct system must be isolated.
Noise Criteria and Wall Isolation. In courtrooms, the most important
consideration is the level of direct sound reaching the listener. Since this sound level
decreases with increased room size and distance between the speaker and the
listener, a lower noise coefficient (NC) value should be specified for larger
courtrooms. See Table 4.3 for specific NC and wall isolation values.
Lighting. Any ballasted light sources providing higher lighting levels must be
carefully selected and placed to minimize the ballast noise. Dimming such lights
should not increase noise levels.
Speech Privacy. In the courtroom, the jury box should be located at least 20 feet
(6100 mm) from the point where bench conferences occur. This provides adequate
privacy for a bench conference with lowered voices. For greater privacy or shorter
distances, a sound-masking system with loudspeakers located at the jury box should
be provided. The system can be activated by a switch on the judge's microphone.
4-62
12/19/97
Previous Page
