Vimpex talks to PE about Voice Alarm (VA) systems – a viable option moving forwards for more complex alarm systems.
In modern buildings, there may be dozens of different types of audible warning specified: fire alarm systems, emergency exit alarms, lifts/elevators, intrusion alarm systems, and each can have their own audible warning device.
In industrial settings, there may also be audible warning devices on production equipment, assembly lines, and on forklifts.
With so many different types of audible warning devices, it can be confusing to building occupants when an alarm sounds.
Is it the fire alarm? An emergency exit alarm? Or has a unit of production equipment just jammed?
To counter these conflicting responses, voice sounders are now an established and effective contribution to voice evacuation systems in large public and commercial buildings, and can be a viable alternative to more complex Voice Alarm (VA) systems.
Behaviour in the Event of a Fire
Research has shown that voice alarm messages result in quicker reaction times compared to when sirens or bells are used.
This has resulted in VA systems becoming more commonplace as the primary means of evacuation in public buildings.
There is some well-documented research into people’s behaviour in the event of fire.
Most striking is the variation in the response to alarm singles:
- 13% of people react in a timely manner to bells
- 45% of people react to text information
- 75% of people react in a timely manner to voice messages
Further research shows that people’s behaviour varies dependent on the environment and, in an emergency, they may exit the building using the same door they used to enter.
The use of a clear voice message greatly increases response time and provides the opportunity to advise occupants of the safest emergency route.
All Voice Systems Are Not Equal
It has become too habitual for specifiers to use standards such as BS 5839 Part 8 (Voice Evacuation Systems) and the applicable directives of NFPA 72 as catch-all standards when voice evacuation is identified as a necessity.
In fact, specifying voice sounders for use in a voice evacuation system designed under the auspices of BS 5839 Part 1 can, in many instances, satisfy the key features of a Part 8 system or NFPA without the cost or complex design process associated with full-blown VA systems.
Much to the disdain of VA system manufacturers, there are many fire systems in the field with more than a hundred voice enhanced sounders on complex systems giving fully synchronised, multi-message announcements in a clear, unambiguous manner.
The Message is Clear
Arguments against the use of voice sounders are dissolving.
With multiple sounder circuit synchronisation, up to seven pre-recorded messages are available.
Plus, with growing ranges of voice sounders constantly being introduced, the message is clear that voice sounders are intelligible, effectively loud enough and can be easily integrated into new and existing fire alarm systems.
It is important to note that piezo-driven voice sounders do not provide nearly as clear and intelligible messaging as those that use more traditional capsule-driven loudspeakers.
This is because a piezo device is designed to maximise output at a pre-determined frequency and not a relatively broad frequency range as in products like the Vimpex Fire-Cryer.
The Vimpex Fire-Cryer range of Voice Sounders is a good example of how voice technology is proving to reduce delay and response rate in evacuation times.
In its simplest form, the Vimpex Fire-Cryer is an electronic sounder capable of delivering clear, intelligible and synchronised voice messages and tones.
Requiring just two wires, a positive and a negative, it can deliver 24VDC to any one of the Fire-Cryer family of voice sounders. It can also be retrofitted to existing conventional sounder circuits.
Voice Sounder System Design
The first task of any fire alarm design is to agree the evacuation strategy and whether there is any requirement for staged or phased evacuation.
Then, the designer must ensure agreement with the client and the end user as to the choice of messages and preceding attention-drawing tones to be used in the system.
The choice of messages is extensive and, with seven messages available in a single sounder, a fire alarm system can be expanded to include a range of inputs.
These could include bomb alerts, terrorist threats, coded warnings, water leakage alerts, class change announcements, system tests, ‘all clear’ announcements, machinery shut down warnings, health and safety reminders, general alert messages and, of course, fire alarm messages.
The potential is huge and, with the trend for fire evacuation systems to be used for general evacuation and public safety systems, the use of multi-message voice sounders is set to boom.
Multi-Message Switching
Although voice sounders are basically conventional fire alarm sounders that play pre-recorded messages, the sounders need to know what message to play and when.
In order to switch from message to message, a switching interface is installed on the sounder circuit.
This is interposed between the control panel (or sounder module, if on an analogue system) and the rest of the sounder circuit.
The bell circuit provides power for the primary or ‘life safety/fire’ message, whilst an auxiliary power supply – sometimes from the panel, sometimes external – powers the switching interface and the extra auxiliary messages.
Both sounder circuits and auxiliary power supply must be rated to provide current for all sounders and any strobes on the circuit.
Monitoring of the sounder circuits is not affected and the panel’s recommendations on resistance should be maintained.
Synchronisation
A concern of VA systems designers and installers of VA systems is that voice sounders cannot be synchronised.
This is an unfounded concern as there are two ways of ensuring that all circuits are synchronised: by ensuring that sounder circuit controllers are synchronised, or by ensuring that all switching interfaces are linked.
Most switching interfaces will only provide outputs for two or maybe four sounder circuits.
Should more be required, additional interfaces can be used. Some switching interfaces make the job of extending circuits very simple by providing zone extension cards.
For more information on Vimpex, visit: www.vimpex.co.uk.
