As a first option to attenuate vibration problems in the different systems, the engineers in charge of vehicle acoustics and vibrations chooses to place masses strategically to absorb the vibratory energy of the resonance. The effect of these masses is two-folded as, on one hand, they move the frequency of resonance of the system towards a lower value and therefore outside the excitation range, and on the other hand, in the case of the system being excited by a frequency coincident with the new frequency of resonance, the value of the amplitude would be smaller.
Within the selection of materials used specifically for these functions IFF´s or Bitumen pads are well-known. These are plates of bituminous material (asphalt masses) that are placed in zones of the vehicle which are susceptible to have an annoying vibration behaviour (ceiling, doors, ground). For the positioning and definition of these masses, the manufacturers have developed a methodology that is based on an analysis of sensitivity of the modal solution of the structure.
Although it is a correct strategy from the vibratory point of view, the actual technical trends in automobile sector advise against this type of solutions. The addition of mass and the addition of an extra cost at the time of assembly the vehicle can lead to a high cost in the maintenance of the vehicle. The amount of energy that is dissipated in this type of material is proportional to change in speed squared.