Monday’s Friday Reads – 26 August 2019

1. Re the Wired article about sound damage to human hearing. Firstly, dB is a numeric ratio, it’s dbA which is a measure of sound intensity.

   I would have thought that any measure of damage to human hearing should be a cumulative measure of the excess energy from the soundwaves that can cause permanent hearing loss.

   For example, if there are 10 seconds at 90dBA in your 3 minute journey, this would be an excess of 10dBAs. I guess TfL could put such official numbers on a tube map so the public could make informed decisions about where such noise exists.

   From the graphs I have seen, almost all of this excess noise is caused by non-regenerative breaking, so there might be a workable solution to sorting it out.

2. Brian Butterworth: I have not seen the graphs you’ve seen but based on observations travelling around the network i’d say that high noise levels mainly comes from two sources:

   1) Squealing on very tight curves (eg Bank Central line) or
   2) Rail corrugation (erudite description here: http://railmeasurement.com/assets/docs/090709-JRRT-corrugation.pdf); this does seem to be an issue on parts of the Jubilee line extension, the Central line between Liverpool St and Stratford and parts of the Victoria line.

   Braking doesn’t seem to be a particular issue although there is sometimes some squealing as the friction brakes take over from the dynamic brake at low speeds, but not of an intensity or duration that is more than irritating!

3. Just an anecdote, having commented on the over-100dB sections on the Northern line last week, I overheard a conversation on a Thameslink train a couple of days ago in which one person said they always go on TL now, incurring a longer walk at the destination, specifically to avoid “that noise” between Euston and Kentish Town. For anyone who thinks I’m being over-dramatic about it, it’s worth a special trip if you haven’t heard it. To get the full top-whack experience, stand next to a lowered (as they always are) car-end window when passing through the disused South Kentish Town station (either direction will do). I defy anyone to come away and say it’s acceptable.

   At least the Wired article confirmed that TfL have stopped any further rollout of the offending rail fastenings. It’s a bit late, as the noise on the initial bit towards Euston (Bank branch) was just as loud a long time before they inflicted us with a lot more of it further north.

4. From my own experience, the JLE has always seemed much noisier than any other bits of the tube. I had wondered whether the larger tunnels amplify the noise in some way. It seems to be getting worse, although that might equally be me being more sensitive to it

5. @100ANDTHIRTY

   The article with the graphs in was in the Economist. https://www.economist.com/graphic-detail/2019/08/12/londons-tube-is-worryingly-noisy

   My personal measurements of train velocity for the various lines is in this document – https://ukfree.tv/styles/images/2019/Work%20out%20train%20speeds.pdf

   I suspect one of the issues about excessive noise is that is that it is, at each point in time, cumulative. Reducing the level to below 80dBA may only require one form of mitigation.

6. I think noise levels on parts of the network ARE unacceptable, you can see people in genuine discomfort. It’s the high peaks that are a relatively new development, as the tube has always been noisy. Surprised that the noisiest section was between West Finchley and Finchley Central, seeing that that section is in the open.

   The Bakerloo line, due to the 72 stock I imagine, seems to have the highest “base level” of noise, the roar on this line though not uncomfortable is ever present, and makes conversation very hard.

7. Hasn’t the tube always been noisy? It’s the rest of the world which is getting quieter – electric taxis, hybrid buses, quieter cars and lorries in general. On rails, the old A/C/D stock had opening windows and noisy compressors resembling a diesel engine, whereas the new S7/S8 stock with their sealed windows are much quieter.

   Perhaps the solution is to line the tunnels with a sound-absorbing material, though there may not even be space for that.

8. The “Take a ride on your own tiny train” seems to be about an organisation that trespasses on tracks.

9. To be honest, it is quite unclear to me what the Tiny Train article is going on about, and whether trespassing on tracks is part of it. But it should not need saying that, if it is, such a thing would not in any way be endorsed by London Reconnections.

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