Characterizing Wind Turbine Acoustic Emissions at WiValdi: A Field Study on Directional Sound Propagation and Amplitude Modulation

Kurzfassung

This paper presents a one-month unsupervised acoustic field campaign conducted at WiValdi, a research wind farm in Krummendeich, Germany. A single permanent sound monitoring station was deployed at distances of 2 and 6.4 rotor diameters from two modern multi-megawatt wind turbines, enabling directional analysis of sound propagation and revealing clear amplitude modulation (AM) patterns linked to the blade passage frequency (BPF). In order to isolate turbine-generated sounds from ambient noise, an advanced data filtering approach was applied, combining statistical descriptors, wind speed thresholds, and AM prominence criteria. The filtered dataset exhibits strong agreement with high-signal-to-noise reference measurements from a concurrent short-term emission campaign, validating the effectiveness of the proposed methodology. This study demonstrates the feasibility of using a single monitoring station in an open field, when supported by a robust data filtering approach, can reliably infer directional sound characteristics and AM patterns under real-world conditions, despite inherent limitations in noise immunity and spatial resolution. A follow-up study is underway, deploying a multi-station array at WiValdi to enable high-fidelity mapping of sound directivity, quantification of propagation effects, and validation of low-noise blade designs. These efforts will strengthen the scientific foundation for assessing AM in wind turbine noise and support the development of more robust, standardized measurement protocols for future regulatory frameworks.