A comprehensive approach to airborne low-frequency acoustic field measurement using a drone-based system

The ability to map sound fields using airborne acoustic measurement drones opens up new opportunities for both engineering and research applications. In this study, we systematically evaluate the feasibility of drone-based acoustic measurements. Laboratory tests demonstrate that drones are well suited for low-frequency noise measurements, which are challenging for ground-based measurement systems due to the large spatial dimensions of typical noise emitters. We have developed a prototype drone system based on a correlation method between two microphones. The airborne system is validated with a controlled outdoor experiment that uses a self-calibrated low-frequency reference source. The system is capable of measuring radiation patterns and estimating the sound power level of a reference source with a deviation of less than 0.75 dB from its calibrated value following the ISO 3744 procedure. The mapped sound fields further enable source reconstruction and efficient characterization of far-field radiation. One possible application is the acoustic characterization of large energy converters, illustrated here through airborne measurements of noise produced by a wind turbine generator. Airborne acoustic measurements can, therefore, offer capabilities relevant for the commissioning and planning of industrial sites as well as for the validation of atmospheric sound propagation models.