There are two types of vibration the free vibration and forced vibration. Vibration testing is typically done using the random or sine tests. . Understanding the vibration helps to determine the structural needs of buildings and roads, for example, during an earthquake.
The random test is considered to be a closer replicate of the actual environment, such as a road and moving vehicles. The sine analysis shows a single frequency and the tests are usually preformed for assessments of structural response of the devices under test. Most vibration testing is done in a single device under test axis, even though most world vibrations occur in different axes at one time More info: Vibration Testing