Amplitude Modulation: More exciting than you’d think

Photomontage of the Den Brook project

There was an important High Court Judgement on wind farm noise on May 25th this year which somehow slipped past my radar: I’ve just caught up with it. It’s likely to be a headache for wind turbine operators, but it may save a lot of headaches for local residents.

When the appeal by Broadview on my local wind farm, Low Spinney, was heard in Market Harborough, the protest group AWFALS  sought to make a case, and to demand a planning approval condition, based on the “thump” caused as the blades of turbines sweep past the supporting column.  This type of noise is known technically as “amplitude modulation”.

The argument of Broadview on behalf of the industry was interesting.  They said that amplitude modulation didn’t occur to any significant extent, and therefore there was no point in having a condition on it.  The AWFALS view was that if Broadview were right, then the condition could do them no harm.  But if Broadview were wrong, then the condition on amplitude modulation would be an important protection for local residents.  The Inspector sided with Broadview on this point, handing a victory to the industry.  (The impression I have is this is what Inspectors regularly do — they seem to regard it as their job to ensure that Chris Huhne gets his turbines, and never to consider the real and reasonable objections of residents).

But there is another contentious planning dispute around the wind farm plan at Den Brook in Devon.  There, objector Mike Hulme, supported by noise consultant Mike Stigwood, took this particular issue to the High Court, where the Law Lords ruled the other way.  The ruling said, inter alia, “If amplitude modulation is unlikely, then it is equally unlikely that it would be necessary to enforce the condition …..the condition imposed is of a precautionary nature”.

There now seems to be a realistic prospect that a wind farm found to breach the amplitude modulation condition could actually be closed down.  And the industry has had a warning shot across its bows: we must hope that it will start to reject sites too close to dwellings because it is unable to meet the condition.

Meantime South Cambridgeshire Council has passed a motion requiring that turbines have a 2 km set-back from dwellings — a condition that Lincolnshire approved some time ago.  Slowly, little by little, barriers are being put in place.  In the Den Brook case, the implications could be far-reaching.

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