Page 1
Introduction
The GA904 Electronic Orange is a system for use where amplified sound
could give rise to complaints about noise from neighbours. If the sound level
should exceed the trip level the unit will remove power from the stage or
amplifier system. The orange beacon warning light gives an indication of the
noise level to enable the stage manager or the person in control of the
amplifier output to regulate the sound level below the maximum permitted.
A problem associated with amplified sound is the possible environmental
effects outside the premises and the annoyance and nuisance caused to
adjoining residential premises. In this case external levels are related not only
to the internal levels but also the degree of insulation offered by the structure
of the premises.
This can only be changed by costly and often prohibitive changes to the
building. However, it is clear that for any given structure, control of the
internal sound levels will affect the external levels.
In many cases these external levels may well be the determining factor for
levels inside the building and for this reason the GA904 was designed. Castle
Group invented the first “Electronic Orange” Entertainment Noise Controller in
1971, since then it has become an industry standard, recommended by
many Local Authority Environmental Health Officers.
The GA904 has been developed from the original “Noise Limiter” and now
offers even more control.
Instrument Description
The sound in the entertainment venue is detected by an independent
microphone installed in the body of the room in such a way that the sound
detected is predominantly that of the amplifier system output.
Once installed, the microphone signal is received at the control box of the
GA904 and processed by a sound measurement system. If the pre-set trip
level is approached a warning is given, set by the warning level control, to
allow the operator to turn the volume down. If the trip level is exceeded the
trip timer will switch power off the amplification equipment for a pre-set time.
After this pre-set time the power will always be restored regardless of the
sound level unless you are using the manual reset function (see page 10).
The unit itself has a built in 20 second mute function to ensure this. When the
mute time has expired, the unit will resume measuring the sound level and
the power will be cut if it is not turned down. The process would repeat if the
volume is not turned down. The reason for the mute function is to allow the
operator of the amplifiers or discotheque time to respond by manually turning
