The electrification of vehicles poses significant challenges to automotive manufacturers, particularly in the production of electric traction drives. Winding concepts such as Hairpin, I-pin, or X-pin technology are increasingly relying on the use of rectangular copper wires instead of round wires for stator windings. Here, a large number of connection points between individual winding sections have to be realized by laser welding and are crucial for overall functionality and product quality. To ensure the quality of each of these joints, process

monitoring with in-process capable sensors is increasingly being pursued. This paper focuses on whether the quality of the welds can be monitored using an optical microphone. Therefore, the acoustic emissions of the welding process are analyzed and correlations between the acoustics and features of welding quality, such as pore formation or cross-section area, are investigated. For this purpose, the study is based on a design of experiments, which provides welds of varying quality. While welding, the optical microphone records the signal curve as well as the energy curve of the sound as relevant process parameters. The quality of the welds is subsequently determined using 3D X-ray computer tomography analysis. Some of the features derived from the signals were found to significantly correlate with the weld quality. The findings demonstrate that optical microphones can serve as effective sensors for monitoring weld quality, however establishing clear correlations between acoustic emissions and specific welding errors remains challenging and needs to be improved for enhanced industrial applicability.