2 February 2024

Himly’s Xavier Sanchez-Roemmele and Josep Simona have been carrying out research on wind farm amplitude modulation noise, which is planned to be published in the coming months.

Amplitude modulation (AM) is a distinct characteristic of noise caused by some wind turbines, which can increase noise annoyance. The research carried out by Himly suggests that current guidelines may not adequately address the adverse impact of amplitude modulation, and highlights the need for further research and for encouraging an urgent revision of the guidelines.

These conclusions appear to be aligned to those of a recent report commissioned by the former Department for Business, Energy and Industrial Strategy (2023) – where two types of amplitude modulation were described. The first, also known as ‘blade swish’ or ‘normal AM’, is referred to as being most prominent at close range to the turbines and in crosswind. The second type, “non-TEDCAR-AM”, has a lower frequency sound character and can be present at longer ranges and over different directions from turbines. It has been linked with reported noise disturbances and is sometimes described as ‘whoomphing’. Non-TEDCAR-AM can be affected by a wide range of interacting factors, including turbine operational parameters, topography, atmospheric effects, refraction, inflow turbine variation, and turbine wake effects.

Analysing the noise effects of wind farms is one of the services provided by our noise experts at Himly. Please contact us if you would like to discuss your case with us.