As mentioned earlier, typical noise regulations specify some combination of absolute dB levels and relative (above ambient) dB levels. Because most noise regulations predate wind turbines, there's an implied assumption here that wind turbine noise is essentially the same as any other noise and can be regulated with similar rules. Unfortunately, there's growing evidence that the "whoosh" is unnatural enough and pervasive enough that it requires special treatment. The combination of low frequencies and the pulsing character of the noise is not easily blocked by walls or alternative sounds, like running a fan. Most people can adjust to noises over time, but there's growing indications that people never adjust to wind turbine noise - in fact for some it gets worse over time.

Amanda Harry is an English MD who started noticing medical complaints several years ago, and gave a questionnaire to a number of residents who lived close to turbines. All of these turbines met the English noise rules (ETSU-R-97) and yet there were widespread complaints at a number of projects.

Eja Pedersen documented the responses of residents to different levels of wind turbine noise and compared these reactions to other equally-loud sources of noise. She found that wind turbines create more complaints at lower levels than any other source, i.e. traffic, trains, planes etc., as summarized by the chart below.

• Van Den Berg article, 2.3mb, Perspectives on Wind Turbine Noise.
• Pedersen Paper, 0.6mb, Human Response to Wind Turbine Noise
• Pedersen and Waye, 0.1mb, Perception and Annoyance. Above 35 dBA, annoyance grows more quickly with turbine noise than any other kind
• Pedersen Paper, 0.4mb, Turbine Noise, a Review
• Frey Paper, 1.0mb, medical effects
• Harry Paper, 0.4mb, Wind Turbines, Noise and Health
• Pierpont Paper, 0.3mb, medical effects