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

Creative Commons License CC BY NC ND This work by Dan Russell is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License . Based on a work at http://www.acs.psu.edu/drussell/demos.html . Additional information about using this content is available at http://www.acs.psu.edu/drussell/Demos/copyright.html .


The content of this page was originally posted on August 16, 1999. The animations and the content on this page were updated on August 4, 2025.
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Coupled Oscillators

animaiton of a red mass-spring system (on the left) connected with stretchy string to a blue mass-spring system (on the right) having the same frequency. The two sine-wave curves (red on top and blue on bottom) show the amplitude as a function of time for the two mass-spring systems.

Two identical oscillators (having the same natural frequency) are coupled together by a elastic spring. One mass is displaced from equilibrium while the other mass is kept at the original equilibrium location; both masses are released from rest. The resulting oscillation trades energy back and forth between the two oscillators -- the amplitude of the first oscillator will gradually decrease (eventually coming to a stop) while the amplitude of the other oscillator gradually increases (reaching a maximum) and then the reverse happens.




Here is a video of the coupling behavior of two identical pendulums connected by a soft spring.


Below is a an earlier version of the coupled pendulum demonstration -- but with a music soundtrack in the background . . . the soundtrack is a 1974 performance of "Swing Low, Sweet Chariot" by jazz saxophonist Sonny Rollins Jazz Quintet with Rufus Harley on the bagpipes, but so many people complained about the annoying bagpipe music that I made a new version of the video (linked above) without the music in the background.