There have been a number of articles in the press about the sound levels on London Underground. Usefully the Economist managed to provide a useful graph of measurement, thus
However, whilst the diagrams show (in heavy highlight colour) the problem sound area, the article simply highlights the peak level between stations, and this isn’t the real issue when it comes to Health and Safety.
So, I propose each inter-station link has a value z, which is the decibel-minutes of excess noise.
Lmax is defined in ISO 17025 as the max value of Leq for each second interval.
85dbA is the “safe limit” taken from http://www.hse.gov.uk/noise/noise.pdf
The use of minutes means that the results will be usable integers, rather than hundreds.
Any journey where the level never exceeds 85dbA will get z=0
A 300 seconds at 90dBA will get z=25
A 60 seconds at 115dbA would be z=30
For fairness the measurements should be taken in the centre carriage at 1 meter about the floor. The main issue I have with data collection is finding calibrated equipment, as the apps out there don’t have an external reference. Any ideas?
The articles were: