Abstract
One of the main purpose of the acoustic analyze at cars is to improve passenger and driver comfort. This aim can be obtained by reducing noises generated by the vehicle or by phonically insulation of the source (engine or transmission) or of the cabin. Recent results in the field of the active control of noises are published in [2], in which the effects of using a sound absorption wall on an active noise reduction system when in the analyzed zone a significant source of noises is introduced. In the case of absorption, the energy of the waves produces out of phase shifts in the material’s structure, being consumed in internal frictions. Nowadays there is a large variety of sound absorption materials produced by diverse companies, most of them under the form of panels. The use of sound absorption materials is limited in the case of engines and working machines by the necessity to impose other characteristics, such as heat transmission coefficient, in order to ensure the efficient cooling of the enclosure sound insulated. An alternative to the use of such materials is the realization on the surface of the sound proofing panels of geometrical configuration that will disperse the incident waves instead of reflecting them.
Keywords: noise, sound proof, sound absorption, waves, engine