Anyone dealing with installed machinery encounters instances where structural resonance amplifies machine vibration. The machine may meet stringent specifications in one instance but exceed acceptable vibration levels in another. A good understanding of natural frequencies and the tests necessary to identify them will help solve these vexing situations.

Natural frequency is the frequency at which a system tends to oscillate in the absence of any damping or driving force. The phenomenon of driving a system with a frequency equal to its natural frequency is called resonance. A system being driven at its natural frequency is said to resonate.

When an object vibrates at a frequency equivalent to its natural frequency the vibration of the amplitude increases significantly, which could lead to irreparable damage.

Learning objectives:

  • What are natural frequencies and why do they exist?
  • How to conduct a basic bump test with a single channel analyzer
  • What is a modal analysis and what additional information does it provide?
  • Outline of related tests and concerns