ASA Adjudication on RidgeWind Ltd

Ad

A circular for a proposed wind farm development.

Issue

The complainant challenged whether the claim:

1. "Modern turbines are surprisingly quiet.  You can stand underneath a turbine and hold a conversation without having to raise your voice" gave a misleading impression of the noise generated by wind farms because the sound pressure and acoustic effects of the turbines meant that noise was experienced further away, and

2. "There are strict guidelines on wind turbines and noise emissions to ensure protection of residential amenity" was misleading and implied that there would be no noise affecting local residents.

CAP Code (Edition 11)

Response

Ridgewind said the claims were based on the content of a British Wind Energy Association (BWEA) article on wind farm noise. They pointed to a previous ASA adjudication where a very similar claim to that in point 1 was investigated and found not to have breached the Code.

Ridgewind sent comments on the complaint from Hayes Mckenzie Partnership (Hayes), a leading independent noise consultancy company with particular expertise in noise from wind turbines and wind farm sites. Hayes said they considered it was not misleading to state "modern turbines are surprisingly quiet" because many people were genuinely surprised by what they heard.  Hayes also said it was true that you could stand underneath a turbine and hold a conversation without having to raise your voice.  They said the ad did not refer to noise levels further away but it was true that noise levels at residential properties were considerably lower than at a turbine. On point 2 Hayes said the leaflet did not claim that there would be no noise; it merely stated that it was strictly regulated to ensure protection of residential amenity and that that was true.

Assessment

1. Not upheld

The ASA noted a previous investigation had examined the issue of whether a normal conversation could be held beneath a wind turbine and found that the claim was unlikely to mislead. We noted the current complainant believed the noise emission footprint of a wind turbine meant that the greatest incidence of noise would fall a distance from the turbine and therefore the claim gave a misleading impression as to the general noise emissions from wind turbines.  We also noted the complainant cited a recent study by the University of Salford on behalf of the Department of Business Enterprise and Regulatory Reform (BERR), entitled Research into Aerodynamic Modulation of Wind Turbine Noise, which, they believed cast doubt on the previous decision.

We understood from the previous adjudication that, although readers might expect the base of a turbine to be the noisiest location, it was sometimes possible to recognize small increases in sound at a short distance from it because some noise was emitted from the turbine hub and carried by the wind.  However, because it was noted that the noise increases would not be so significant as to make normal conversation problematic and because the distances involved did not fall beyond the established limit for the distance a turbine should be sited from residential dwellings, we concluded the claim was unlikely to mislead readers in relation to noise levels in general.

We noted the recent University of Salford study had been commissioned by BERR in response to another study, which raised questions arising from the incidence of aerodynamic modulation (AM) by studying data on UK wind farm sites. We understood that  most wind turbine noise emissions were aerodynamic sound generated by pressure variations within the air, which fluctuated at acoustic frequencies as they passed the turbine blades. We understood that AM was a specific feature of that noise that could be recognized as a repetitive 'thumping-like' sound, although we also noted the complainant pointed out that one of the findings of the University of Salford study was that the causes of AM were not fully understood at the present time and that it was not possible to predict its incidence.

We noted the University of Salford study reviewed the literature on AM and included a specific section on its propagation. It noted a study that found AM was not equally loud in all directions as it was radiated primarily from the outer part of the downward moving blade in a downward direction. The reviewed study indicated that AM was often heard directly beneath the turbine and not further away due to the weaker nature of the horizontally propagated noise. We noted the review also indicated that AM generally conformed to the model of noise decreasing with distance from the turbine. We noted, however, the University of Salford study also raised the issue of a phenomenon where AM noise appeared to travel and be heard at considerable distance from the turbines.  The study highlighted the fact that such occurrences could not yet be explained fully and that further studies were required.

Although we acknowledged the unexplained aspects of AM that deviated from the accepted model of noise emissions generally decreasing with significant distance from the turbines i.e. at the point such noise emissions reached residential dwellings, we considered that the claim was likely to be understood by readers as an example to demonstrate wind turbine noise was not as noticeable as they might expect.  We noted the University of Salford study concluded that the incidence of AM, whilst not fully understood, was found to be a factor for complaints about noise in only a few instances. Furthermore, we noted the study found that the incidence of AM and the number of people affected was very small. We therefore considered that the issues with AM could not be regarded as representative of the general characteristics of wind turbine noise. We concluded that the ad was unlikely to mislead.

On this point, we investigated the ad under CAP Code clauses 3.1, (Substantiation) and 7.1 (Truthfulness) but did not find it in breach.

2. Not upheld

We noted wind turbine noise emissions were regulated under the terms of the ETSU-R-97 report, entitled The Assessment and Rating of Wind Turbine Noise, which was administered by BERR. We understood that ETSU-R-97 did not require that all noise emissions be inaudible and we noted instances of official complaints against specific wind farm sites and the anecdotal evidence of those in close proximity experiencing disturbance due to noise emissions. We also noted several criticisms of ETSU-R-97, for example, its reliance on average sound levels, rather than taking into account extreme variations, and its lack of provision for AM. We considered, however, that the objections were focused on specific issues and noted the established position of BERR and acknowledged experts, such as Hayes Mackenzie, was that generally the guidelines were robust.  We also considered that the claim that there were "strict guidelines on wind turbines and noise emissions to ensure protection of residential amenity" was unlikely to lead readers to infer that the protection offered by ETSU-R-97 would ensure that there would be no noise emissions. We therefore concluded that the claim was unlikely to mislead.

On this point, we investigated the ad under CAP Code clauses 3.1, (Substantiation) and 7.1 (Truthfulness) but did not find it in breach.

Action

No further action necessary.

Adjudication of the ASA Council (Non-broadcast)