Ever since the moment when the energy was generated in the source medium until it reaches the end user of the vehicle, energy must go through a path that can be solid (vibrations) and /or aerial (sound). Energy may transfer between both media several times. There are three ways to prevent this energy from reaching the receiver:
ISOLATION: isolation is the capacity of an element to reduce the energy (vibratory or acoustic). Isolation is the difference between the vibratory energy that affects a certain element and the energy that the element gives to its surroundings. We test that the energy that occurs in the sources mentioned before does not reach the rest of systems in the automobile (body, cockpit). If the vibration reaches any of the elements by a solid route, we will regard this as requiring vibratory isolation, whereas if the vibration reaches that element through the air, we will then speak of sound insulation.
DAMPING OF VIBRATIONS: The damping of vibrations is the quality by which a system in a determined vibratory state decreases its amplitude of vibration until it stops.
ABSORPTION: Sound absorption is a capability that all types of materials have in order to turn the sonorous energy that affects them into heat. This is similar to what occurs with the damping of vibrations, however this is a case of acoustic energy in an enclosure.