Acoustic monitoring of wind turbine noise  emission with spatial filtering arrays for  continuous wind park investigations
Creators: name: Wenzel, Tobias Morten
Publisher: name: Zenodo
Year: 2024

description: The emitted noise sound is part of the concerns about wind parks but also contains information about the wind turbine operation and potential failures. Continuous acoustic monitoring in wind parks has the potential to oversee noise levels and process sound signals related to failures at a wind turbine, e.g., at the blades' surfaces or gearbox faults. For investigations into wind turbine sounds, a spatial assignment of noise sources is needed to separate sounds from turbine parts from background noise. In this research,the aim is to develop systems and techniques for applications in noise emission monitoring and spatial sound assignment at wind turbines in wind parks. To fulfil this aim, a significant part of this research project was focused on the development of a suitable microphone array monitoring hardware that is robust enough to withstand outdoors continuous environmental conditions for wind park acoustic measurement deployment. Microphone arrays are due to their arrangement of multiple microphonescapable of spatially separating sound sources. The array development includes a suitable microphone unit, an acoustically transparent protective membrane for the microphones, the design of an outdoor array containing 64 microphones and the firmware for the processors in the system. A new development was necessary because there are neither suitable measuring instruments nor designs for robust acoustic arrays available in literature or on the market. The appropriate wind park application of the developed hardware was made to record wind turbine noise with the boundary conditions of noise recording standards. The results from the applied array hardware were compared to the current standards for wind turbine noise measurements, which do not cover the continuous observation at wind turbines. The data collection campaign was performed during two seasons of the year in the wind park. In 9 weeks of wind park operation, a total of 76 hours of acoustic, environmental and wind turbine operation data wascollected in different conditions. This data has been analysed for noise emission monitoring and have been spatially filtered for acoustic turbine part observation. This work successfully showed that anacoustic array can be deployed long-term in a fixed location to continuously monitor noise emissions in a wind park for the first time and proved that the results of this approach are comparable with the current standard. Secondly, it has successfully demonstrated its performance in combating noise emissions by being used in a wind farm for 9 weeks and under various environmental conditions and delivering reliable noise level data. Thirdly, it has shown that automated spatial filtering can be used to localise noise signals to specific parts of the wind turbine which can be further analysed for fault detection. The research showed that with an advanced robust acoustic array monitoring system the high demand fornoise investigations at wind turbines can be served.