Synergizing mode decomposition and numerical analysis for creating sound sources with known power output: Application to an outdoor infrasound source

• The study conceptualizes and tests a sound source with precisely known power output. • The synergy of experiments and prior numerical simulations was utilized. • The developed source is omnidirectional and can be used indoor and outdoor. • Application is straightforward, and uncertainties align with established standards. • The developed sound source enables in situ calibration of acoustic sensors. Accurate sound sources are essential for calibrating outdoor acoustic sensor networks used in technical and environmental monitoring. This study investigates a ducted loudspeaker with flush-mounted microphones as a sound source with known power output and uniform radiation. The power outflow is determined using a mode decomposition method taken from duct aeroacoustics that enables quasi real-time source strength estimation in indoor and outdoor environments. For low-frequency applications, a single-microphone method is proposed that integrates mode decomposition with prior numerical analysis. The approach is validated in a reverberant field, showing agreement with ISO 3741, ISO 3744, and sound intensity methods. Furthermore, directivity patterns are determined via experiments and a numerical model. Error analysis highlights the importance of an accurate reflection coefficient at the duct termination in achieving an accuracy within 2 dB, which is comparable to established standards. The method is successfully applied to generate an outdoor infrasound source with known power output and uniform hemispherical radiation, making it suitable for calibrating inaccessible sensors, such as CTBTO stations or distributed microphones in smart cities.