When using evacuation alarms in cinemas and theaters we have the great advantage of ideal acoustics in most cases. That is, of course, a condition for such an environment. However, a focus point is the speaker power.
Cinemas and theaters usually have high ceilings and the transmission path is long. To have a sufficient audio level on the audience, a high efficiency speaker is required. The requirement is that the evacuation signal overrules the environmental noise with at least 10dB.
‘This needs a lot of attention during the design stage’
The evacuation signal should always overrule the environmental noise. In a cinema or theater, the sound will usually have a value of around 90dB. An evacuation signal should have at least an value of 100dB. With a ceiling height of 10 meters, the minimum speaker level should be an amount of 112dB to 115dB.
Most speakers have an SPL value from 90 to 105dB. This value is the value at 1 meter distance. Special speakers for these applications are therefore required. These speakers must also comply with the standards that apply here, the EN54-24.
‘System Designs for these application need a lot of attention and is work for specialists’
A comprehensive measurement is necessary when commissioning the system. A proper report should therefore be a part of the delivery.
In particular new generations evacuation systems can be equipped with Digital Signal Processors to optimize the sound. Do not be tempted by the argument that evacuation can be done by the public address system/stage installation. These installations are not designed for evacuation and do not have the technical principles necessary for evacuating at all.
Think of the power supplies with uninterruptible power supplies and amplifier redundancy. Furthermore, the fire department will first disable the power supply of the building in case of an emergency to avoid short circuits. In that case, a public address system would not do anything.
In our article on public address systems versus evacuation systems you can read more about this.