Tutorial on Excitation of Structures: Shakers and Instrumented Hammers

Shakers and instrumented hammers can be useful tools for practicing noise control engineers. By exciting a test structure with a known force input, the vibration characteristics of a structure (such as natural frequencies, damping ratios, and mode shapes) can be easily determined. Different test structures require different excitation techniques. Choosing an appropriate excitation method for a given situation can be difficult, especially for complicated structures. In this tutorial, practical tips on sensor selection, fixturing, and technique are shared. First, a general comparison of shakers and instrumented hammers is made, with examples of test articles that favor one or the other. Then, tips for choosing an appropriate hammer and hammer tip based on the test article and frequency range of interest are offered. Common issues and challenges with hammer excitation are explored. Finally, options for shakers, force sensors, and excitation signals are discussed.