Basically, a voice alarm system is a standard PA system in 100 V line technique with one or more connected microphones. However, since it is part of a building's security concept there is more to be taken into account. A voice alarm system helps people to save themselves. In an emergency, they must be guided out of the danger zone calmly and purposefully, something which can hardly be accomplished with a simple audible alarm. A well planned voice alarm system can calm people down and guide them straight to the exit. It is often relevant in case of fire, yet it is also applied in other dangerous scenarios. That's why voice alarm systems are part of fire protection regulations.
Not every installer and planner is certified to fully plan a voice alarm system, to mount it or to put it into operation. Still, it is important to know the basics. Only then you can advise customers and plan PA systems comprehensively. If you include in your planning right from the beginning which features the system has to provide, you will be able to combine a background PA application with ceiling speakers e.g. with a voice alarm system.
There is no general answer to this frequent question. The EN 54 is a standard for fire alarm systems and therefore does not change. However, when you have to install a voice alarm system according to EN 54 is regulated differently, because this is part of building law and in Germany building law is federal state law.
It is one indicator for planners or planning installers, whether the building has to comply with the federal state's regulations for places of public assembly.
The regulations for places of public assembly of Germany's federal states differ, sometimes even significantly. The appropriate building authority has the final say. The following standard values are often decisive for the requirement of a voice alarm system:
- A place of public assembly with an area of at least 1,000 square metres
- A place of public assembly where more than 3,000 people regularly stay during daily operation
- Sales rooms and areas that are bigger than 2,000 square metres
The relevant standards for voice alarm systems
|The general standard for fire alarm systems, which also includes project phases and planning phases for voice alarm systems. Planners and installers will have to be certified according to this standard if they intend to plan and implement a voice alarm system.
|DIN VDE 0833
|Planning, installing, expanding, changing and operating alarm systems and voice alarm systems in case of fire
|Power supply of fire alarm systems and voice alarm systems
|Components for voice alarms and voice alarm control centres in fire alarm systems
|Components for voice alarms, speakers for fire alarm systems
A statutory voice alarm system has to meet 6 central requirements to be accepted by a fire prevention officer:
- A voice alarm system requires 2 separate power sources. Both have to be able to supply power to the voice alarm system independently. If the regular power supply is disrupted, a second independent power supply has to take over immediately. Thus, it is highly unlikely that the voice alarm system is without power in an emergency.
- The cable paths of the voice alarm system have to be supervised. This can be achieved e.g. by a pilot tone. Pilot tones are sounds humans cannot hear with which the voice alarm system supervises itself autonomously. While we do not notice the tone, the system itself, however, detects if a single speaker or a speaker line within the system cannot be controlled anymore.
- The voice alarm system is connected to the fire alarm system which controls it in case of an emergency. For this purpose, there has to be an approved and certified interface.
- It has to be be possible to trigger the voice alarm system manually at all times.
- A voice alarm system has to be operational continuously, without any downtimes.
- The system has to reproduce a minimum sound level of 10 dB over the ambient noise level. Therefore, you should rather plan voice alarm systems with an extra speaker to achieve high speech intelligibility.
A certified specialist has to measure the ambient noise level with a calibrated device. Electricians without additional certification are allowed to choose and mount speakers as well as lay cables. Launch and approval by a certified specialist will be required if a voice alarm system complying with a fire alarm concept is mandatory.
You can integrate the implementation of a voice alarm system at least into your rough concept for a PA application.
For builders or subsequent operators of a building, a well-documented, comprehensive list of individual planning steps is relevant as it helps to work on an equal footing.
Security level I: Buildings with an area of less than 2,000 square metres and a capacity of less than 200 people. Damaged cabling may lead only to failure of one single fire compartment or alarm zone, but not of an entire floor.
Security level II: Buildings with an area of more than 2,000 square metres and a capacity of more than 200 people. A malfunction in an amplifier or a channel must not result in failure of the voice alarm in an alarm zone. Thus, an A/B line cabling is mandatory. Speech intelligibility (STI) must never be lower than 0.5 (CIS > 0.65) and the sound pressure level must never decrease lower than 3 dB.
Security level III: This security level applies to buildings with high default risks, such as power plants or safety-critical industrial facilities. Here, all standards of security level II apply, expanded by a complete additional voice alarm system, i.e. the individual system has to be redundant. If one alarm system fails, another complete system will be available.
How to measure speech intelligibility
The indicators for speech intelligibility are the STI (Speech Transmission Index) and the CIS (Common Intelligibility Scale). An STI of more than 0.5 or a CIS of more than 0.7 is sufficient for all standards. If one speaker zone fails, an STI of 0.45 must still be reached in all areas. To test speech intelligibility, electricians require a certification and an appropriate measuring device.
For full protection it is required that all parts of the building can be alerted. Besides standard rooms this also includes lifts, sanitary facilities, utility rooms and storerooms. For partial protection a PA application is only required in those parts of the building that are also zones of the fire alarm system. Whether other areas have to be included depends on how you interpret the fire protection concept. Discuss this with the responsible architect or fire protection officer.
During this step you have to cooperate very closely with builders, subsequent users and fire protection officers. You require the building's ground plan and some peace and quiet. Check the room sizes and calculate the number of speakers. For this, we provide a general rule in our article on ceiling speakers. You can also include basic background music in your PA application, because a voice alarm system can easily reproduce background music, too.
The voice alarm control centre has to be in a fireproof and, if possible, dry room. All buttons and displays have to be labelled clearly. The junction box and the system cabinet are also in this room. Please consider if several microphone stations, i.e. microphones connected to the voice alarm system, are useful.
Due to the 100 V line technique you can simply add up power ratings (W) of speakers and thus choose an adequate amplifier. A 150 W amplifier, for example, could provide power for 2 zones with 25 3 W speakers each. However, we advise against planning amplifiers whose power output exactly matches the number of speakers. First, an amplifier running on the limit can grow hot quickly and second, distortions can occur. That's why we even recommend a 'buffer' of approximately 20%.
Conclusion: Voice alarm systems are PA systems with additional requirements
You can make a note of these planning steps conceptually, before you start to plan and to implement a voice alarm system or you can incorporate it straight into the consultation with the builder or subsequent operator. That way you not only generate higher project security but also maximum transparency. However, you should always keep an eye on which certifications are required for the implementation.
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