Localization and sound power estimation of noise sources in industrial plants using coherence scanning holography

Reducing noise emissions from industrial plants requires an initial step of localizing key contributing sources. Acoustic cameras are pivotal for quickly identifying these sources, yet challenges persist in low-frequency source localization and presenting results for effective impact assessment. This contribution introduces Coherence Scanning Holography—a method based on scanning the sound field by means of a rotating linear microphone array covering a measurement surface with diameter of 2.5 m for low-frequency source localization from 125 Hz. The underlying sound imaging method compensates for Doppler distortions in the moving microphone signals and evaluates coherence spectra with a non-moving reference microphone to compute an acoustic image. For analysis, a method quantifying sound power contributions from specific regions in the optical image is presented. Comparing sound power metrics of the full optical field of view with metrics of regions of interest enables users to quickly rank source contributions and assess the impact of reducing these contributions on total sound power. In complex scenarios, preliminary investigations can be streamlined with a few measurements from diverse angles, expediting the problem-solving process with confidence. The method is exemplified through the analysis of sound emissions from a production plant.