INFORMATION: As the extent of station public address coverage has increased, so have complaints from residents living nearby. Technology is available to automatically sample background noise before an announcement is made and adjust the volume to ensure it is heard without causing too much disturbance beyond the station, but many of these systems cannot cope with changing levels of background noise, for example as a train passes.

ASL Safety & Security’s Dynamic Ambient Noise Sensing processes the signal to distinguish ambient noise from the announcement itself, continuously optimising the volume level during a broadcast. This allows default volumes to be adjusted to much lower levels than before, improving the passenger experience as well as the lives of nearby residents. It is designed to be fitted to both new and existing public address networks.