Reducing Sound Radiation of an Automated Transmission by Means of Viscoelastic Multilayer Damping

Brazilian automotive industry has reached a high level of competition and production, and in this scenario noise radiation is a very important factor in which quality, cost and comfort have to meet consumers' impressions of a vehicle. Engineers face today difficult challenges when it comes to improvement of noise emissions: solutions should be fast, cheap and effective. This work presents a recent study to reduce shell noise radiation from an automated transmission mechanism using two solutions of structural damping: modification in the material of the noise source and attenuation of shell movement by using surface patches of viscoelastic sandwich. Although traditionally applied to whole radiating surfaces, the second solution demonstrates that portions of the material applied in proper selected locations are very effective for reduction of shell noise, therefore enabling the usage of smaller sizes of viscoelastic material instead of complete coverings. That fact represents an enormous advantage in terms of cost of application for the material and provides the NVH engineer a very useful tool to cope with sound radiation problems.