Only 15 of 521 sites have a noise problem caused by turbine blades stalling when wind speed drops – and software can fix it

Only about 3% of windfarms in the UK are likely to produce a low-frequency sound that can be heard up to a kilometre away.

The thumping "whoomph"-like sound, produced when the blades on a turbine partially stall because of changes in wind speed and direction, is about as loud as the noise from a single carriageway road, according to a review of evidence on the effect.

Opponents of windfarms often cite noise concerns along with aesthetic complaints, but the problem is shown to be infrequent and can be easily fixed with software changes, said trade body RenewableUK, which commissioned the report. The noise – known as other amplitude modulation – is different to the normal "whooshing" sound that can be heard close to turbines as they cut through the air, known as amplitude modulation.

The review looked at previous reports, including a 2007 University of Salford paper that found of the 133 wind turbine sites around the UK at the time, four were definitely creating the sound, and eight were possibly connected to it but could not be proved conclusively. "It can be read that a similar percentage could apply now," said a RenewableUK spokesman, suggesting at least 15 of the current 521 wind turbine sites are affected by the problem.

But the report, by the Temple Group environmental consultancy, also said that the problem is easily solved by changes to the software running the turbine, which rectifies the stalling problem. Local authorities that receive complaints about such noise can force turbine operators to rectify the issue.

RenewableUK's deputy chief executive, Maf Smith, said: "The research shows that this only affects a limited number of windfarm sites, and when it does occur it can be resolved using a software fix which controls the angle of the turbine blades. It's right that the wind industry should take the lead in investigating issues like this when they arise."

The report concluded that it was "not feasible to predict" at which locations the noise might occur. Its authors concluded the main causes of the sound were "an aerodynamic effect called "stall" and the associated separation of wind flow from the upper surface of the turbine blade."

Polls have repeatedly found the majority of the British public are in favour of wind power, but onshore windfarms have become increasingly political contentious, with Tory MPs calling for cuts to subsidies. Onshore wind subsidies were cut 10% in April and further cuts were announced earlier this month, leading RenewableUK to say that some marginal community turbines were no longer likely to go ahead.