Noise Source Localization On a Small Wind Turbine Using a Compact Microphone Array with Advanced Beamforming Algorithms: Part I - A Study of Aerodynamic Noise from Blades

Small wind turbines, which are increasingly being used near residential areas, sound louder than their larger counter parts due to their close proximity to dwellings. Previous noise measurements on small scale wind turbines were performed using single microphones which only provide an overall estimate of the total noise emitted from the wind turbine. For wind turbine manufacturers trying to address the issue of noise reduction through design, the knowledge of the dominant noise source location and source mechanisms is important. This information can be obtained using a microphone array and sophisticated beamforming algorithms. In this paper we use a compact microphone array to locate and quantify noise sources on a small (8 kW) Viryd 8000 wind turbine. The results from the microphone array show that we are able to successfully locate and separate both mechanical and aerodynamic noise on the wind turbine using advanced deconvolution algorithms such as TIDY, CLEAN based on Source Coherence (CLEAN-SC), and Deconvolution Approach for Mapping Acoustic Sources (DAMAS). For frequencies above 4000 Hz, aerodynamic noise appears to be the dominant noise source and for frequencies below 3000 Hz, mechanical noise from the nacelle appears to be the dominant noise source.