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Effect of Beading on Radiated Noise
Abstract:
In the automotive industry, the use of beading is widely spread. Beads are primarily used to stiffen the floor and dash panels. The aim is to reduce vibration levels and hopefully at the same time reduce radiated noise. Beading has a positive effect close to the first panel mode's natural frequency however it can have a negative effect at all other frequencies. Typically, engineers assume a radiation efficiency of “1” (one) over the whole frequency range for simplicity or lack of available implemented formulation in their simulation tools. This assumption directs the investigation at reducing the vibration levels only. This approach can be misleading because even though radiation efficiency tends to “1” (one) above coincident frequency it is not the case below coincidence. While increasing stiffness reduces vibration levels, it also increases radiation efficiency. This can yield to higher levels of radiated noise.
This paper presents a comparison between panels with uniform cross-section and beaded panels in two different configurations: i) Academic frame and plate case and ii) Automotive floor. Vibration levels, radiation efficiency and sound radiated power are presented for all cases. Different types of beadings are compared and conclusions are drawn as to whether these beadings really reduce radiated noise.