Peter Able wrote:
On 21/02/2021 17:29, Recliner wrote:
Basil Jet wrote:
On 21/02/2021 17:06, Recliner wrote:
Anna Noyd-Dryver wrote:
Roland Perry wrote:
In message , at 10:11:15 on Fri, 19 Feb
2021, Recliner remarked:
Basil Jet wrote:

"The Battersea Branch will be the first extension to the Underground
network since the Jubilee Line Extension from Green Park to Stratford"

Since https://en.wikipedia.org/wiki/List_o...round_stations
is sortable by opening date, forgetting
https://en.wikipedia.org/wiki/Heathr...inal_5_station is a major
facepalm.

You're quite right, of course, but I suppose they don't regard the
additional Heathrow station as an extension.

It's approx 2km, so rather more than just a new station.

Topographically it's almost identical to the Battersea Branch (~3.5km)
but maybe the writer thought it was like T4?

T4 involved 6.1km of new single-track tunnel.


Those almost straight new tunnels are among the loudest on the whole LU
network. It's almost painful. Does anyone know why?

If you mean the T5 tunnel, I imagine they're the only part of the tube
constructed with NATM.


Parts of the central HEx station famously use NATM, but I don't think any
of the Tube or HEx running tunnels used NATM. They look like normal deep
bored tube concrete ring tunnels, as used on the JLE and probably the
Battersea extension.

Those T5 tunnels are fairly shallow and have heavy airliners parked or
taxiing above, so I wonder if they use a more sturdy construction than
usual tube tunnels?


Might be of interest?

https://eave.io/wp-content/uploads/2...-full-data.pdf

Thanks, it confirms my observation (though I'm surprised a few other
stretches are shown as even noisier), but I wonder what explains it? These
are new, smooth, straight concrete tunnels, probably with a slightly larger
diameter, so one might expect them to be smoother and quieter than
century-old steel tunnels.

On Mon, 22 Feb 2021 22:57:48 -0000 (UTC), Recliner
wrote:

Peter Able wrote:
On 21/02/2021 17:29, Recliner wrote:
Basil Jet wrote:
On 21/02/2021 17:06, Recliner wrote:
Anna Noyd-Dryver wrote:
Roland Perry wrote:


If you mean the T5 tunnel, I imagine they're the only part of the tube
constructed with NATM.


Parts of the central HEx station famously use NATM, but I don't think any
of the Tube or HEx running tunnels used NATM. They look like normal deep
bored tube concrete ring tunnels, as used on the JLE and probably the
Battersea extension.

Those T5 tunnels are fairly shallow and have heavy airliners parked or
taxiing above, so I wonder if they use a more sturdy construction than
usual tube tunnels?


Might be of interest?

https://eave.io/wp-content/uploads/2...-full-data.pdf

Thanks, it confirms my observation (though I'm surprised a few other
stretches are shown as even noisier), but I wonder what explains it? These
are new, smooth, straight concrete tunnels, probably with a slightly larger
diameter, so one might expect them to be smoother and quieter than
century-old steel tunnels.

I'd have thought that a tunnel with smooth concrete walls was just
about the noisiest possible space, the diametric opposite of an
anechoic environment.

ISTR that Victoria Line getting some flack in 1969 with people hoping
that the first new line for 60 years would have demonstrated some
progress in noise reduction. It hadn't and it seems little has changed
as the Jubilee and T5 prove.

I wonder how Crossrail will pan out?

I find that noise map curious. It suggests that open air sections are
in some cases over 80dB, noisier than some tunneled sections. That
doesn't match with my experience. When entering the tunnel at
Southgate or Arnos Grove, for example, the noise levels subjectively
jump considerably.

Trolleybus wrote:
On Mon, 22 Feb 2021 22:57:48 -0000 (UTC), Recliner
wrote:

Peter Able wrote:
On 21/02/2021 17:29, Recliner wrote:
Basil Jet wrote:
On 21/02/2021 17:06, Recliner wrote:
Anna Noyd-Dryver wrote:
Roland Perry wrote:


If you mean the T5 tunnel, I imagine they're the only part of the tube
constructed with NATM.


Parts of the central HEx station famously use NATM, but I don't think any
of the Tube or HEx running tunnels used NATM. They look like normal deep
bored tube concrete ring tunnels, as used on the JLE and probably the
Battersea extension.

Those T5 tunnels are fairly shallow and have heavy airliners parked or
taxiing above, so I wonder if they use a more sturdy construction than
usual tube tunnels?


Might be of interest?

https://eave.io/wp-content/uploads/2...-full-data.pdf

Thanks, it confirms my observation (though I'm surprised a few other
stretches are shown as even noisier), but I wonder what explains it? These
are new, smooth, straight concrete tunnels, probably with a slightly larger
diameter, so one might expect them to be smoother and quieter than
century-old steel tunnels.

I'd have thought that a tunnel with smooth concrete walls was just
about the noisiest possible space, the diametric opposite of an
anechoic environment.

ISTR that Victoria Line getting some flack in 1969 with people hoping
that the first new line for 60 years would have demonstrated some
progress in noise reduction. It hadn't and it seems little has changed
as the Jubilee and T5 prove.

I wonder how Crossrail will pan out?

I find that noise map curious. It suggests that open air sections are
in some cases over 80dB, noisier than some tunneled sections. That
doesn't match with my experience. When entering the tunnel at
Southgate or Arnos Grove, for example, the noise levels subjectively
jump considerably.


Yes, many of those reported noise levels surprise me. I do have a decibel
meter, plus there's a phone app, so I might do some checking once travel
resumes.