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Elizabeth line testing ways of banishing its "ghosts in the walls"

ianvisits.co.uk

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Re: Elizabeth line testing ways of banishing its "ghosts in the walls"

#11

Post by SEMW »

mgaunard wrote: post #3
londons_explore wrote: post #2

Don't clean stuff... Just hide the dirt!

I would guess that the kind of plastic resin that's used for the walls reacts with heat and can easily be permanently marked.

It's glass fibre reinforced concrete (GFRC). Very much doubt it's heat-reactive, suspect it's just oil & dirt on a somewhat porous surface (so cleaning properly is labour-intensive, stickers are cheaper)

Re: Elizabeth line testing ways of banishing its "ghosts in the walls"

#18

Post by Tor3 »

kozhevnikov wrote: post #7
donalhunt wrote: post #4

Earlier quoted context omitted.

Funnily, the same approach is often used for acoustic / noise issues. Add music / other sources of sound to try and mask the acoustics issue (unsuccessfully).

Isn't it the basis of active noise cancelling? It's pretty successful.

No, active noise cancelling isn't about masking noise with sound, active noise cancelling takes the original noise and mixes it back 180 degrees out of phase. The net result is zero noise, when done perfectly. In practice it's almost like that (for the frequencies covered by the noise cancelling equipment - in an airplane it's like the background noise just.. turns off. What's left is typically people talking. It's easier to hear the flight attendants).

If instead it was by adding sound then it would defy the purpose. I use active noise cancelling because if I don't I'll hear a noise in my head for weeks after a long-haul flight (I have tinnitus in one ear which makes it even worse).

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