Reducing track noise

[route:oxford]

Not really, given how clunky their planning server seems to be at times. And none of which gets away from the fact that your statement was not true.

Perhaps that's where I've noted the content.

Ah well. At least you've highligted that The Green lied outrageously about the risk of shadowing from 36 metres away.
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Something durable, inert, and with the necessary energy-absorbing properties, capable of being fastened securely to a substrate, and preferably light in weight.

You forgot energy efficient to manufacture and recycle.

 

[krus_aragon]

Vegetation is an excellent sound absorber.

Many people described as railway veg, however, are often noisy. :P

 

[Trog]

HUSH rail?

 

[jopsuk]

Vegetation is an excellent sound absorber.

At my previous job, which was a factory site, the environment agency could only carry out perimeter sound measurements on calm days as it didn't take much wind for the sound generated by trees to completely overpower the industrial noise. Trees are very, very noisy.

Something durable, inert, and with the necessary energy-absorbing properties, capable of being fastened securely to a substrate, and preferably light in weight.

"I've no idea, so I'll just list the properties. It'll only take you clever materials chaps a couple of days yes? Oh, don't forget cheap"

 

[RAGNARØKR]

At my previous job, which was a factory site, the environment agency could only carry out perimeter sound measurements on calm days as it didn't take much wind for the sound generated by trees to completely overpower the industrial noise. Trees are very, very noisy.


"I've no idea, so I'll just list the properties. It'll only take you clever materials chaps a couple of days yes? Oh, don't forget cheap"

Who said it could be developed on a shoestring? The size of the potential market determines how much it would be worth spending on R&D. Given the amount of screening one sees around, the figure must be substantial.

However, nobody would spend anything on further development until the concept of sound absorption as close as possible to source had been proven. That was what my question was about. To start to think about materials is way down the line.

Just so as to give you the obvious pleasure you will take in rubbishing the suggestion, I would envisage a possible embodiment of the concept as a synthetic rubber-like material bonded to a rigid substrate, to be installed in a similar way to the safety guards used where third-rail electrification is installed. Yes, I am aware that the railway environment is very hostile.
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Perhaps that's where I've noted the content.

Ah well. At least you've highligted that The Green lied outrageously about the risk of shadowing from 36 metres away.
--- old post above --- --- new post below ---


You forgot energy efficient to manufacture and recycle.

Yes, the closer to the sound source, the smaller the energy absorption device will need to be.

 

[krus_aragon]

At my previous job, which was a factory site, the environment agency could only carry out perimeter sound measurements on calm days as it didn't take much wind for the sound generated by trees to completely overpower the industrial noise. Trees are very, very noisy.

Would you agree that, despite a frequently higher noise level, trees produce a more acceptable noise? I can't recall anyone complaining to me about a noisy tree.

But whatever the auditory qualities of trees, I don't think anyone should seriously consider installing rows of leaf mulch factories along our railway tracks!

 

[Ploughman]

HUSH rail?

We suggested the use of HUSH Rail for a job at Guiseley in the early 2000's but were told it was not permitted for use and even if approved it was not available.

I think the noise reduction is due to the lower depth of the web rather than anything else.
It was not the noise reduction that we were thinking of but the reduced height of the rail to improve structural clearances that we were considering.

 

[dviner]

Yes, the closer to the sound source, the smaller the energy absorption device will need to be.

(Note - I am not an expert on sound or the mechanics thereof)

The closer to the sound source, the smaller the device needs to be, however, the energy of that sound would be much greater than it would be further away. Therefore, you would be asking a lot more of that device, with a subsequent increase in its cost.

 

[edwin_m]

We suggested the use of HUSH Rail for a job at Guiseley in the early 2000's but were told it was not permitted for use and even if approved it was not available.

I think the noise reduction is due to the lower depth of the web rather than anything else.
It was not the noise reduction that we were thinking of but the reduced height of the rail to improve structural clearances that we were considering.

The only Hush Rail I ever saw was at West Jesmond on the T&W Metro back in the 80s (don't know if it is still there). The reason was apparently again to do with clearances, specifically dropping the top of rail by a couple of inches to give level boarding without having to raise the platforms or do anything to the roof of the subway.

Being less deep I imagine it is also less strong, so shorter life as well as more risk of breakage as well as being non-standard. One of these is probably the reason if it's banned from the main line.

 

[Peter Sarf]

How about fitting the noise reduction to the train. If the sound reduction has to be close to the source than that would be cheaper. So until trains are longer than the gaps between them the amount of materials required on-board will be under 50% of the amount required on the tracks !. That should also reduce the aesthetic impact.

Now how about fitting loudspeakers as near as possible to the offending sound source - each bogie perhaps ?. Then transmitting a reverse of the offending sound. I recall that if the reverse wave can be created accurately then the resulting sound could be negligible.

 

[gimmea50anyday]

would I be criticised if I made the serious suggestion that people give the proximity of a railway line some consideration when buying a house?

Heared the story of an apartment block in Sheffield built next to a well known nightclub?

Residents started to complain anout the noise from the nightclub and got it shut down as a result. The venue had been there for over 30 years before the apartment block...

http://www.theguardian.com/music/20...oardwalk-uk-live-music-venues-shut-developers

 

[Peter Mugridge]

How about fitting the noise reduction to the train. If the sound reduction has to be close to the source than that would be cheaper. So until trains are longer than the gaps between them the amount of materials required on-board will be under 50% of the amount required on the tracks !. That should also reduce the aesthetic impact.

Now how about fitting loudspeakers as near as possible to the offending sound source - each bogie perhaps ?. Then transmitting a reverse of the offending sound. I recall that if the reverse wave can be created accurately then the resulting sound could be negligible.

That's known as "Active noise suppression" but I'm not sure it's got beyond the early testing stage anywhere yet; it's still pretty much theoretical. I first saw the idea being discussed about 30 years ago in relation to aircraft noise and it hasn't been put into production yet.

I think the problem is that to work properly it needs the "opposite sound" to be issued from the exact same point as the original sound that you are trying to cancel. If you have a linear sound source, then you're going to end up with 50% of the distance with no sound at all and the other 50% with double the sound thanks to interference patterns amongst the noise waves. This effect could get interesting with multiple emission points...

 

[edwin_m]

That's known as "Active noise suppression" but I'm not sure it's got beyond the early testing stage anywhere yet; it's still pretty much theoretical. I first saw the idea being discussed about 30 years ago in relation to aircraft noise and it hasn't been put into production yet.

I think the problem is that to work properly it needs the "opposite sound" to be issued from the exact same point as the original sound that you are trying to cancel. If you have a linear sound source, then you're going to end up with 50% of the distance with no sound at all and the other 50% with double the sound thanks to interference patterns amongst the noise waves. This effect could get interesting with multiple emission points...

This is of course the basis of "noise cancelling headphones", but they only have to cancel the noise in one location which is a lot easier.

It's only really useful for fairly steady sounds, because the system has to predict the sound before it happens in order to emit the "anti-noise" at exactly the same time. So probably not much use for rail joint noise for example.

 

[Peter Sarf]

This is of course the basis of "noise cancelling headphones", but they only have to cancel the noise in one location which is a lot easier.

It's only really useful for fairly steady sounds, because the system has to predict the sound before it happens in order to emit the "anti-noise" at exactly the same time. So probably not much use for rail joint noise for example.

The one location would be the train or parts thereof - as distinct from the track. Perhaps the leading wheels could be used to predict what the following wheels/bogies are going to generate from the same point on the track. But I agree that the sound does not necessarily come from the point of wheel/rail contact but is generated via the resulting vibrations in the rail along a length of rail.

Have to wonder how much effort the roads are putting into noise abatement ?. When I stayed near a road junction the noise would be more than on a plain road where vehicles are not slowing down or accelerating. Which is why I would like the speed bump outside my house to go away !. All night we get car brakes then engine noise. But often, if its a driver who does not care, then they fly over the bump quite often with a sudden load thud or scrape of car underbelly !. Only sensible drivers who were not speeding slow down for the speed bumps. My point is is this rail noise that serious - especially as the railway was often there first.

Selhurst depot has signs up reminding the visitors to the new estate adjacent that diesel engines are running all night. Its right by the fuelling point. How long before the railway has to close up shop overnight. The best pub garden in Croydon has to close at 22:00 because of complaints from the flats overlooking it - the pub even objected to the planning proposal for the flats !. Another pub that was the local live music venue has closed because of complaints from the newly built flats next to it. So I guess the railways are being picked on.

 

[najaB]

That's known as "Active noise suppression" but I'm not sure it's got beyond the early testing stage anywhere yet; it's still pretty much theoretical.

It's actually in use quite a bit. One example is the Q400 which uses noise cancellation technology to be significantly quieter inside than comparable turboprops.

I think the problem is that to work properly it needs the "opposite sound" to be issued from the exact same point as the original sound that you are trying to cancel.

It's more that you need a speaker/transducer that is as loud as the sound you want to cancel and they aren't cheap and require a lot of energy.