Sound beaconS

Various public address systems exist to help facilitate the evacuation of users through emergency exits, including sound beacons which can be found in certain tunnels.

Figure 1: Sound beacons above an emergency exit

These sound beacons are located in the part of the tunnel open to traffic and have the following objectives:

• raise the alarm to users if there are no other audible alarm devices in the tunnel,
• provide clear information and instructions to users,
• help the users locate emergency exits in the event of smoke,
• encourage users to go to an emergency exit and use it.

It is important to be able to adjust the sound level of these beacons in order to prevent reverberation phenomena and inaudibility.

The information that is announced can be:

• pre-recorded,
• in real time (provided by an operator from a control room),
• a mix of the two previous modes.

In cross-border tunnels, announcements may be made in the language of each country on which the tunnel is located.