London’s Docklands Light Railway (DLR) is piloting a public address system at its Island Gardens station which promises to make it easier for passengers to hear messages, without blasting out the neighbourhood.
Developed by the DLR with electronics consultancy Gilden Research, Smartsound automatically adjusts the volume of PA announcements so that messages can always be heard, even with constantly varying levels of background noise.
Through the use of passive infra-red (PIR) detectors, the system only activates loudspeakers next to people for whom the message is intended.
Prior to the installation of the system, the volume of PA speakers at DLR stations was on two settings – day and night.
During the day, messages for passengers were drowned by excessive background noise and at night, local residents complained about the noise, although the PA was at a lower output level.
Smartsound solves these problems in three ways. First, sampling microphones mounted at the station monitor background noise. To prevent the microphones from confusing background noise with PA announcements, the Smartsound device is suspended for the duration of each message. The volume of each announcement is at a constant 8dBA above the level of background noise.
Secondly, PIR detectors, which work like any sensor-based intruder alarm, only allow messages to be broadcast through speakers where they find nearby passengers.
The PIR device prevents speakers being switched on or off for the duration of a message, preventing partial messages being broadcast and confusing passengers.
Finally, the existing loudspeakers along each platform have been replaced with more lower output speakers.