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This paper deals with the results of an investigation of moulded cases such as acoustic deflectors housing noisy equipment of the vehicle. The main advantage of the deflector is to decrease the level of noise, but the phenomenon of self-excitation is important, too, because it becomes a new source of noise. Readjustment of the vibration modes spectrum is possible by creating special structural variations, which increase the internal dissipation of energy of the vibrations in the deflector material. This approach is related to the introduction of design variables, the kind of material or to the choice of the points of fixation. The principal indication of a vibration mode of such a structure as a deflector is the number of nodal points. This characteristic gives the possibility to select several groups of modes, which are effective from the viewpoint of decreasing vibration amplitudes. Other possibilities are related to the means of active vibroinsulation.

This paper summarizes the results that were obtained from investigations of vibrations of cover- and box-shaped elements that cover assemblies of automobiles and are intended to diminish noise. The problem is that the elements in hand can appear to be the additional source of vibrations. For the elements fastened on the automobile body, the conditions for vibration excitation and recommendations for design are made more precise, at the same time keeping in mind that the main function of mentioned elements is not the reduction of noise. Our approach consists of three main directions: modifying properties of material, changing structure of elements and recommendations for choosing the preparation of its fixation points.

The paper presents a study of active car suspension and the ways for vibration damping improvement. Road irregularities are the main factor affecting ride comfort. The aim of suspension is to improve these undesirable effects by isolating the car body from wheel vibrations induced by uneven terrain. The main objective of active suspension system is to reduce motions of the sprung mass. Damping input is a force applied between the sprung and unsprung masses. Main suspension damping element is the FESTO pneumatic muscle (a.k.a. artificial muscle). A frequentatives characteristic of artificial muscle was determinate and possibilities work in frequencies characteristic excitation from new and wearied asphalt pavement is analyzed.

In order to solve the acute problems of the design of the body structures of vehicles more complicated models of the main aggregates and systems of transport means are created moving forward from the common recommendations. The constantly increasing safety requirements essentially changed the design criteria. Thus the accurate estimation of the frame's structures under loads very important as well as search for the new solutions both while using the modern technologies and rationally solving the design problems. In order to avoid the arising modeling difficulties and calculations problems the simplified reduced digital models should be discussed. These models adequately describe the real structures with the help of which one can more flexibly operate in such situation.