Siren wails hard on ears

Published: 3 December, 2010

• LIVING in the urban jungle of London is never going to be quiet, but wouldn’t life be easier on the ears without the constant background wail of sirens? I know our emergency services need a vehicle and pedestrian warning system – time is very much of the essence – but at what cost?

Do sirens have to produce such an incredibly loud tonal sound to be effective?

In April 2008, the Noise Abatement Society placed a massive LED display at the busy junction of Old Street and Shoreditch, which was attached to a sound pressure level meter – activated by the noise from passing traffic. I would have much preferred the LED display and meter to be on heavily congested Euston Road.

I spent a short while watching the readings. From registering at around 56dbs for ambient traffic noise and a blip to 68dbs for a car horn, it then raced to 92dbs as the police nudged their way through stationary traffic. 

The loudest was actually a road sweeper at a deafening 97dbs.

Because of the size and location of the LED display, the occupants of vehicles could see the sound level rise as they got closer, making some aware of the noise their vehicle was emitting, with differing results. A few honked their horn to see if they could make the number change, others just stared at the pretty lights. An ambulance crew blasted their big horn and a British Transport Police van switched theirs off. 

For the first time many drivers and occupants could see a visible record of the noise produced from the vehicle they were in. A few look rather shocked, others not so.

The present emergency sirens use several different frequencies to give warning of their approach. Apart from most ambulances, the vast majority of sirens are not directional, therefore defeating the warning of where the vehicle is approaching from – potentially causing confusion along with noise nuisance. Is there another way?

The Noise Abatement Society (NAS) seems to think so. It is campaigning for emergency sirens to use broadband sound technology – which uses directional white sound – but so far the regulatory bodies are far from convinced. This available technology, which is directional and utilises white sound, has already been very successful with reversing alarms on large vehicles in the NAS’s Quietening the Streets campaign. The decision makers have said they are willing to look at other technologies. In the meantime we are left with the London equivalent of tinnitus.

SIMON LAMROCK
WC1