Prospects and limits of modal damping determination from acoustic signals

Damping determination in experimental modal analysis often is sensitive to the added mass by excitation and response measurement equipment. Thus, acoustic methods e.g. loudspeaker excitation or sound pressure measurements are alternative non-contact approaches but are limited in the precision.This study presents prospects and limits of the structural damping determination by sound pressure measurements. Different experimental modal analysis are done with varying excitation signals. Moreover, radiating rectangular steel plates are compared to hybrid metal-plastic composites with low shear resistant cores such as Bondal of-fering significant structural damping. There, common impact excitation fails for the determination of high modes. Thus, the plates are excited by noise or sweep signals of a shaker. The radiated sound pressure is measured in near field. Finally, damping is determined by the half power points of the magnitude within the frequency re-sponse function.