Acoustics and Vibration Animations

Daniel A. Russell, Graduate Program in Acoustics, The Pennsylvania State University

All text and images on this page are ©2013 by Daniel A. Russell and may not used in other web pages or reports without permission.

The content of this page was originally posted on April 23, 2014.

Waveguides and Evanescent Modes

This is where I'll put some text explaining waveguides, modes, evanescent waves, and phase speed.

The Interactive Waveguide Animation

The animation below shows video clip of a Mathematica Computational Document Format (CDF) animation of a logitudinal wave in a duct being driven at the left end (the source is the red "piston"). The interactive animation may be downloaded (WaveguideModes.cdf) and played by downloading the Free CDF Player from

You can change the driving frequency of the source, and you can change the mode number of the wave shape that the piston is attempting to excite. When the driving frequency is above the cut-on frequency for that mode, the modeshape will begin to propagate to the right, down the duct. How to use the Interactive Animation

Some Observations to Make


  1. David T. Blackstock, Fundamentals of Physical Acoustics, (John Wiley & Sons, 2000), chapter 6-D and 12.