February 26th – The technology of controlling public spaces fascinates me. Footfall monitoring systems, environmental control and public information screens all have their own complex theories and rationales. Even something seeming as simple as a public adress system is complicated in the implementation.

At Birmingham New Street, the public announcements, if one listens carefully, are not relayed universally through every speaker, and there is often a slight timeshift between two announcements on adjacent platforms. The volume of the PA rises and falls locally based on background noise levels measured automatically by a number of units like this, buried in the fascia of the station walls.

I noticed this one this morning as I waited for my train. I thought about how tuned the system must have to be – to echo, resonance, and the synchronisation must have to be just so.

What results are hopefully comfortable, easily heard announcements, that don’t clash and collide with interference from multiple speakers as you move around. This is clearly a very, very sophisticated system, and I’d love to know more about it.