The end of the line

Measuring noise, part 12

If you have dutifully slogged your way through all of the eleven blogs so far in this current series on measuring noise, plus the three that I posted in the second half of May about the effects of speed on noise, you probably feel that you have heard more than enough on the subject from yours truly. If it’s any consolation, I’m feeling a little that way also. However, I make no apologies for the noise blogitis; it will be the one impact of HS2 that will affect the most people and it is a topic on which I feel HS2 Ltd is very vulnerable.

However, please brace yourselves for one last episode. I think that, as we have covered so much ground – well I have and I hope that at least one or two have made the journey with me – it will be useful to summarise the main elements of the case that I have made about the way that HS2 Ltd is tackling noise. So here we go:

  • No evidence is offered in the Appraisal of Sustainability to support the decision to plan on the basis of using wayside noise barriers that do not fully shield the train. No indication is provided as to how the alternative proposal to “control aerodynamic noise through advanced rolling stock design” will be achieved or what the risk is that “mitigating the source of aerodynamic noise” will not prove to be possible by this means (A little bit of magic, posted 17 May).
  • The possible impact on noise annoyance levels of the fast onset rates associated with noise traces from very high speed train passes appears to have been ignored by HS2 Ltd in their investigations, and is certainly not mentioned in the Appraisal of Sustainability (Another thing worth ignoring, posted 21 May).
  • No proper justification is given in the Appraisal of Sustainability for making noise predictions at 360 kph rather than the design speed of 400 kph. No formal undertaking has been made in support of the assurances that have been given verbally that trains will not be allowed to run at higher speeds if the 360 kph noise predictions will be exceeded as a result (“We don’t believe you”, posted 25May).
  • No evidence is offered in the Appraisal of Sustainability to support the 3 dB “reduction in noise emissions at source based on the anticipated noise control improvements in the next generation of high speed rolling stock”. No indication is provided as to how this reduction will be achieved or of the technical risk associated with this assumption (A little bit of magic, posted 17 May, and “We don’t believe you”, posted 25 May).
  • HS2 Ltd has failed in the Appraisal of Sustainability to examine or justify the appropriateness of using the equivalent continuous noise level (Leq) as the sole method of assessing the noise nuisance level despite a growing level of opinion, including by the World Health Organisation, that the results obtained using this approach may not be truly representative of noise nuisance or health effects (Taking a longer-term view, posted 22 Jun).
  • HS2 Ltd has failed in the Appraisal of Sustainability to examine or justify the appropriateness of using A-weighted noise levels despite a growing body of evidence and opinion, including that of the World Health Organisation, that applying this weighting characteristic leads to data that underestimates the noise nuisance and health effects of noise with an appreciable low frequency energy component, as is typical of aerodynamic noise from very high speed train passes (A weighty matter, posted 26 Jun).
  • HS2 Ltd has so far failed to provide the noise contour maps that the Transport Secretary promised would be made available for the public consultation (Pass me the map, posted 30 Jun).
  • By its own admission HS2 Ltd has used a method to predict noise levels (CRN) that requires adaptation to be suitable for use for aerodynamic noise from train passes at speeds of 300 kph and above, but no such adaptation has been made to date and no undertaking given that this work will be carried out (Trust me, I’m an acoustic engineer, posted 4 Jul).
  • HS2 Ltd has made no attempt to quantify the night-time noise nuisance that HS2 will cause, despite the fact that the planned operating hours includes three hours that are specified as night-time by the World Health Organisation and the Department for Communities and Local Government (It’s on the level, posted 8 Jul).

It is the responsibility of HS2 Ltd to ensure that the methodology being used to assess noise nuisance is fit for purpose. It is no defence for HS2 Ltd to claim that it is using standard methods that have been “fine” in the past; ultra high speed trains are a new noise nuisance source that demands a new approach. That HS2 Ltd has produced a technical assessment of noise for the Appraisal of Sustainability that has so many holes in it and questions against it is, to say the least, unfortunate.

And now I promise that the next blog will be on “something entirely different”.

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