Small wind turbine furling noise measurement

Small wind turbine generators (WTG) with power capacities of approximately ten kilowatts (~10 kW) often feature a furling mechanism, triggered when hub-height wind speeds are excessive and present damage risk to the bladed rotor and other components, that rapidly changes the aerodynamics and consequently noise emission character and magnitude. This paper summarizes the results of a multi-week outdoor data collection survey, including overall sound pressure levels (SPL), spectrograms, and short-duration concurrent audio recordings, that quantifies furling noise from a sample 10 kW WTG installed and operating at a measurement distance of approximately 850 feet and under a variety of ambient wind speeds recorded by a nearby National Weather Service (NWS) meteorological station. The survey found furling noise to be distinctive, consistent with descriptions in available literature (e.g., loud "thumping"), and in some cases measurably and audibly dominant--even amidst natural background sources such as nighttime insect song.