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The Sound of Safety

A critical factor in the quest to achieve fire safety is an effective fire safety strategy, and an essential component of this is a strategy for the safe evacuation of the building. Voice alarm systems have been around for the best part of a couple of decades, and there is strong evidence to support the argument that their ability to deliver clear and unambiguous voice messages improves response times, ensures that the safest emergency exit routes are used and achieves an appropriate response to any emergency.

As buildings – and in particular public event arenas, shopping malls, superstores and high-rise commercial, residential and mixed-use structures – become more complex, the ability to control and manage the movement of people to safely in an emergency has become ever more challenging. Raising an alarm can cause members of the public in particular to panic and potentially behave in ways that may jeopardise their own or others safety. However a voice instruction, or series of instructions, tailored to the specific risk and communicating the most appropriate actions to be taken, delivered in a calm and concise manner can reassure them and give clear instructions on what to do.

A spoken message identifies the nature of the problem and gives specific and detailed information to the public. It provides real-time information, giving exact instructions to people who may not be familiar with the surroundings, while also improving management of the evacuation. This may be to exit all areas of the building, to conduct a planned phased evacuation of the building or, in some circumstances, simply to remain in place.

There is ample evidence to show that spoken instructions significantly reduce the time taken to evacuate a building after a fire alarm has been activated, particularly by visitors, delegates or customers who are almost certainly unaware of the building’s fire and emergency procedures. This is supported by a growing body of research that validates the argument that voice messages result in shorter and more reliable pre-movement times in an emergency than a sounder system. This research also indicates that the use of shorter messages helps to reduce the pre-movement times still further.

A voice alarm system also overcomes the problem of different countries using different alarm tones, as there is no universally accepted fire alarm tone across the Asia Pacific region. While a buzzer or bell might be the same in every “language”, there is no way in which its meaning can be instantly conveyed if the building’s occupants are from many different countries and cultures.

Human Behaviour
Human behaviour is a major consideration when addressing the evacuation challenge, so it is important to appreciate the likely actions people will take in a fire to ensure their safety.

Language is important. In Australia, for example, while English is regarded as the national language, as many as 15 percent of the population – around four million people – are believed to speak a language other than English at home. These include Italian, Greek, Cantonese, Arabic and Vietnamese. So a message broadcast only in English may be not only meaningless, it may add to the confusion or panic and be of little more use than a traditional alarm sounder. An option in these circumstances is to broadcast in several languages, one after the other.

Other studies have shown that there is often a high propensity to ignore conventional sounders, that without fairly precise warnings some people will assume that the fire is only a minor event, plus there is a strong universal tendency for people to strive to exit a building via a familiar escape route or the route they took when entering the building, which may unknowingly put them at greater risk. In shopping malls, for instance, being with family members may influence escape behaviour and hence the overall escape time.

Another human behaviour factor that has been thrown up by research is the time it takes from an alarm bell sounding, for the occupants to actually do anything regarding their escape. It has been discovered that pre-movement time can be significant; indeed in some instances, more significant than the distance that would have to be travelled to a safe exit.

Evacuation
In all probability, when assessing the evacuation strategy it may not be possible to make structural changes – such as providing additional exits – to an existing building, particularly in the case of high-rise structures.

While architects endeavour to limit the distances that will have to be travelled to an exit, as a method of limiting the time to escape, it is often assumed that the travel time will form the largest part of the time taken to evacuate the building; which is not always the case. Studies have shown that the pre-movement time referred to earlier can be a significant portion of the total evacuation time; alarmingly, in many cases it can be longer than the travel time. Put simply, people stand around trying to decide what the alarm means and whether it is directed at them, pondering what to do and looking around to see what others are doing.

These pre-movement times have been assessed for a number of different structures and the conclusions are that they can account for up to a staggering 80 percent of the evacuation time. The ability to reduce this pre-movement time with clear and incisive messages can therefore significantly reduce the total evacuation time and is a major benefit that comes with installing a voice alarm system.

Stay in Place
Not that the most appropriate action is always to exit the building; there may be instances where moving to another part of the building or not using particular exits are the safest options. Providing this sort of information is all but impossible with anything other than a voice alarm.

For example, today terrorist threats are all too common and simply sounding a conventional fire alarm can have disastrous consequences by moving people into danger instead of away from it. Indeed, voice communication is vital in terrorist threats as it is difficult to contain areas without this type of system. This is particularly so if the emergency is suspected to involve a so-called “dirty” bomb. In addition to instructing occupants to remain where they are as there is the risk of further detonations outside the building, a voice alarm can also remind people to stay away from windows or evacuate only via an exit away from the danger area.

Voice Alarms
There is plenty of evidence to demonstrate that voice messages are far more effective than bells, buzzers or beacons alone and that in an emergency the public take more notice of spoken words than fire alarm sounders. Independent research has revealed that only 13 percent of people react in a timely manner to bells in contrast with 75 percent who react quickly to a voice message explaining the nature of the emergency.

A voice alarm system can be used for live speech as well as recorded messages; it is a zoned system, and can be used to broadcast timely announcements, along with the option to broadcast background music. The level of manual control offered by the system and the need for live messages as opposed to automated messages is at the heart of the decision on the type of system selected. Another valuable feature is the ability to broadcast “coded” messages that have fire and emergency meaning only to key staff, security personnel and fire wardens.

There are currently a number of variants of voice alarm systems on the market that, generally at least, can be categorised as standalone voice sounders, central rack amplifier systems and distributed amplifier systems. The factors to be taken into account when selecting a particular type of system include the type and size of building and the evacuation requirements, considering such factors as whether or not the building and/or its use or occupancy necessitates phased evacuation or “all out” evacuation.

As was discussed earlier, evacuation from large public buildings can often be very complicated, with any number of fire exits and haphazard signage that can so easily lead to panic and as hundreds – possibly thousands – of people attempt to exit the building. In such situations, a voice alarm system can be installed to deliver appropriate messages that are relevant in different parts of the building. It can, for instance, direct people to the nearest safe exit, instruct them not to use lifts, or advise them to remain where they are as they are not at risk.

Cost is a frequently cited reason for not installing a voice alarm system. However, these cost challenges can be overcome by opting for a voice sounder system, which is lower in cost than a voice alarm system, yet provides more information than a conventional sounder. Such systems are not designed to suit every type of building – they cannot be used for live speech, or to broadcast non-emergency information – and are more appropriate for smaller structures, such as small shops and offices with low ambient noise levels. They automatically play a voice message when the system operates and so are generally easier to install.

Most voice alarm system manufacturers offer the option for bespoke messages, allowing the end user to create their own audio files to be uploaded into the voice sounders. Depending on the system chosen, this may be programmed at the production stage or be manually uploaded by the system user.

Building Design Considerations
Whichever voice alarm manufacturer or system is chosen, its design, citing and installation are of critical importance.

Acoustic performance is an area that requires particular attention, as anyone who has struggled to comprehend announcements in supermarkets and railway station all affirm. It is a field requiring expert guidance for, while a typical commercial building may present few acoustic challenges, the same cannot be said for a shopping mall with atria, or a semi-enclosed stadium. For this reason, on new-build projects, it is often advisable to involve the chosen system supplier/installer at the building design stage, as even floor and wall coverings can make a significant difference to the room’s acoustic characteristics.

Large open structures are likely to reverberate and echo and so the intelligibility of a voice sounder will deteriorate over distance, making it important for multiple voice sounders in the same space to be kept in synchronisation. The shape of the room in which the sounder is installed, any background noise present during the time of an emergency, and a system’s synchronicity all affect the intelligibility of the voice message. Another challenge for the designer of the installation is potential problems with what is known as the “spill over” of sound from one area to another that could create confusion.

Clearly, it is vital that everyone in the building can hear and understand the alarm and know precisely what they should do to exit the building. Occupants need to be able to understand the message, but a loud and distinct message does not mean it will necessarily be understood. Achieving this depends, in large part, on the skilfulness of the installation design and loudspeaker system and the system’s acoustic performance.

 

 

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