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17/05/2013
Spin to noise ratio


New post on beleben


Spin to noise ratio

by beleben

51m document explaining high speed rail noise sources

Despite criticism from the National Audit Office, the Department for Transport is 'kicking on with the development of plans for the High Speed 2 rail scheme', the Construction Index reported.

Alongside the draft ES, the DfT has published a series of design refinements for the HS2 route between London and the West Midlands, for further consultation.

Environmental mitigation measures set out include using technology to cut the noise of the trains, such as by eliminating the gaps between train carriages to boost their aerodynamic efficiency.

Drawing on Japanese expertise, HS2 trains could also be fitted with wheel farings [sic], like on a Citroen DS car, to cut the noise made by the wheels on rails – the biggest source of noise on any electrified railway.

Around 70% of the line’s surface sections between London and the West Midlands will be insulated by cuttings, landscaping and fencing, helping it to harmonise with the landscape.

Earth removed for track laying could be used beside it as noise-absorbing bunds, cutting the amount of earth that has to be transported and therefore reducing the number of tipper truck journeys which create congestion, disruption and pollution.

There is nothing new or 'Japanese technology' about wheel fairings and suchlike; the Great Western Railway used them in the 1930s. And the claim that 'noise made by the wheels on rails is the biggest source of noise on any electrified railway' is also incorrect. At the speeds planned for HS2, aerodynamic noise would be the largest source. Unfortunately, the effects of wheel-level fairings and suchlike would be minimal.

The claim about "cuttings" and noise is also misleading. A cutting is defined by HS2 Ltd as "where the depth of excavation from existing ground down to rail level is more than 1 metre. High speed trains create noise up to, and over, four metres from the ground, with pantograph noise being particularly impactful at high speeds.

BBC radio's You and Yours discussion with Arup's Richard Greer gave the impression that the noise control would largely consist of nothing more than wooden fences. So much for 'hi-tech noise reduction'. In reality, the best way to keep the noise down from 200 mph trains, is the same way as to keep electricity consumption and carbon emissions down -- namely, don't run them at 200 mph.

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