Influence of refraction on wind turbine noise

TL;DR

This paper presents a semi-empirical method to evaluate how wind shear refraction influences the propagation and perceived noise levels of wind turbines, aiding in noise impact assessments.

Contribution

It introduces a model incorporating wind shear refraction effects on wind turbine noise propagation, including the partially ensonified zone, for practical noise level estimation.

Findings

Refraction causes a distinct ensonified, shadow, and partially ensonified zones.

Effective sound power decreases to zero in the shadow zone.

The method provides quick estimates of refraction effects on wind turbine noise.

Abstract

A semi-empirical method is applied to calculate the time-average sound level of wind turbine noise generation and propagation. Both are affected by wind shear refraction. Under upwind conditions the partially ensonified zone separates the fully ensonified zone (close to the turbine) and the shadow zone (far away from the turbine). Refraction is described in terms of the wind speed linear profile fitted to the power law profile. The rotating blades are treated as a two-dimensional circular source in the vertical plane. Inside the partially ensonified zone the effective A-weighted sound power decreases to zero when the receiver moves from the turbine toward the shadow zone. The presented results would be useful in practical applications to give a quick estimate of the effect of refraction on wind turbine noise.