Driving-point mobility and sound insulation of structured sheet metal

Abstract

In lightweight construction, the stiffness of plane sheet metal can be increased by the modification of the sheet metal with structures. The present study aims to determine the sound insulation and excitation properties of such structured metal sheets and the parameters which characterize them. The bidirectional structure of the investigated steel sheets is derived from equilateral hexagons with a bulge, arranged in a honeycomb manner. The acoustic properties of these metal sheets are examined in terms of the driving-point mobility and the sound transmission loss by using the finite element method (up to 16 kHz) as well as laboratory experiments (up to 12.5 kHz).The study shows that the resulting driving-point mobility depends on frequency as well as on structure size. Additionally, it was found that the location of excitation has a notable impact on the resulting mobility spectra. The sound reduction index of the structured sheet metals is similar to that of a plane reference plate for low frequencies up to 4 kHz. In a range of medium frequencies between approximately 5 kHz and 12.5 kHz, the sound reduction index of the structured plates is clearly below that of the reference plate.