A sound limiter, also known as environment noise control systems or noise pollution control system, is fast becoming a requirement in many areas of the UK for the granting or renewal of an entertainment licence. Many local authorities are insisting on the installation of an electronic sound limiter in pubs, clubs, bars, halls, restaurants, health clubs and other entertainment venues as a solution to the growing number of complaints regarding noise pollution.
Legislation is in place to control noise and falls generally into 2 categories, briefly:-
1) Health and Safety at work. In EU countries the law protecting people at work from high sound levels is based on the 1986 EU Council Directive 86/188. Each country has translated this directive into its own law. In the UK this is done the by noise at work regulations (1989). This law is based on the concept of a daily noise exposure. Too loud sounds for a short period or not so loud sounds for a longer period can both give the same exposure. Entertainment venues are places of work and the rules apply there just as in factories.
2) Noise nuisance. This falls under the environmental banner of noise pollution. Local authorities are empowered to control the noise levels in their sufficient to prevent noise nuisnace; to impose any reasonable requirements by the issue of a noise nuisance served under section 80 of the Environmental Protection Act 1990 and to enforce compliance through the courts.
The folowing range of equipment
is suitable for installations where frequent use is likely such as installed
function rooms, music venues etc.
Sentry Mk2 Main Unit
The Sentry system was developed after looking at existing products and addressing their shortcomings. The Sentry Mk2 si the second generation of this product offering more facilities than the original Sentry. The Sentry Mk2 incorporates a measuring microphone inside a the unit making it virtually tamperproof. Provision is made to connect an external microphone if required.
A large illuminated bargraph display is incorporated into the unit. This should be installed in a position where it can be clearly seen so the artiste has full knowledge of the levels at which he is working. If the noise level drives the display to full scale, which is all the green, amber and red lights lit, after a period of time the power will be turned off. The time period is adjustable between 10 to 70 seconds. Power can only be restored manually by pressing a reset button.
The Sentry is used in conjunction with a contactor or relay usually to control mains power. The connection between the two is at low voltages so the contactor can be located in a fuse cupboard and wired to control all the sockets in the vicinity.
The Sentry has a security loop facility which can be connected to a relay controlled by the fire alarm or switches that detect open fire doors or windows to ensure that the soundproofing of the venue is not impaired. Magnetic reed switches similar to the ones used in intruder alarms can be used as detectors. If the loop circuit is open the Sentry will switch off and it will not be possible to reset the Sentry until the circuit is closed.
The Sentry Mk2 also has provision to operate at two different levels, which may be selected remotely or by switches operated by open doors and windows, or an optional time switch. This allows the unit to cater for changes in noise type (e.g. disco or live music) or changes in surroundings (e.g. a venue situated near offices requiring stricter control during office hours.)
The combination of the security loop to switch off completely and the second level function provides for most situations to be catered for.
A counter which is not the resetable is also offered as an option. The counter records the number of times the unit has been reset.
To keep the Sentry system as versatile as possible connectors are fitted which allow the connection of several optional features, including remote reset switches, warning lamps, slave displays, etc.
The Sentry when supplied for entertainment venues can be internally selected to work on a linear or 'C' scale or on Bass. This should be used where Bass, i.e. low frequency noise is the problem. When this option is selected a 300 Hz low pass filter with a 12 dB per octave slope is inserted in the measuring circuit.
||The AVC2 limits sound level by controlling the audio signal on the sound system. Whilst the sound level is below the preset threshold, the AVC2 has no effect. But if threshold is reached, the unit fades the signal in a way that is almost undetectable. The amount of signal reduction being applied is indicated by the LED bar graph meter on the front panel of the unit. The more the signal is increased, the more fading will be applied by the AVC2. If attenuation reaches its maximum, the output level will be reduced by more than the increase in input level so that the effect becomes noticable. A clip indicator is provided to show when the input stage of the AVC2 is being over driven. Reducing the input level will gently release the attenuation being applied by the AVC2.|
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