Characterization of Random Vibration

A mechanical system is said to be vibrating when its parts undergo motions that fluctuate in time. The engineering problems that arise in random vibration usually fall within the following headings: measurement of an existing environment, design of a structure or piece of equipment that is to work in such an environment, and the specification and execution of tests to verify that equipment already built will work in such an environment.. Useful analytical tools for performing these tasks are provided by the theory of random processes, which is an outgrowth of probability theory. The chapter primarily presents the pertinent results of this theory. It discusses how in principle it is possible to give complete probabilistic information about a random process. When for theoretical reasons such information is available, it is a simple task to calculate statistical averages for the process. In dealing experimentally with a random process, the statistical averages are much simpler to measure directly than are the probability distributions which underlie them.