Cambridge-based Tyco Integrated Systems has installed the UK's first PA system for tunnels in the Dartford Tunnel – part of the Dartford River Crossing, which is one of the busiest in Europe.
The new system has been designed to provide high quality voice announcements in the confined space within the twin tunnels, thereby offering full accounts of any traffic 'situations' and accidents up ahead. Such messages can also ensure safe tunnel evacuation in the event of emergencies.
In total, over 200 special loudspeakers have been mounted along the tunnel ceilings to achieve uniformly high sound levels of over 100 dB in each tunnel bore.
Due to headroom restrictions, both the size and positioning of the speakers was highly important – the selected low profile speakers provide the same height clearance as the existing lighting units. They also feature a narrow sound opening designed to avoid the reverberation problems normally experienced in enclosed areas.
The system passed all intelligibility tests for drivers both in and out of their cars, such that messages can be heard anywhere in the tunnels. Each of the tunnels is divided into six individually-addressable zones, with messages deliverable to any zone or group of zones.
In operation, the existing fibre optic network transmits audio and data to equipment racks located in two 'vent' rooms. From these rooms, audio and data is fed to zone switching units which in turn feed the amplifiers that drive individual speakers.
Tyco Integrated Systems – Enquiry 108
Source
SMT
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