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Acoustics and Vibration Animations
Daniel A. Russell, Ph.D. Graduate Program in Acoustics The Pennsylvania State University All text and images on this page are ©2004-2011 by Daniel A. Russell and may not used in other web pages or reports without permission. | ![]() ![]() |
A string which is fixed at both ends will exhibit strong vibrational response only at the resonance frequncies
The vibrational pattern (mode shape) of the string at resonance will have the form
![]() | When a fixed-fixed string is set into vibration by plucking it, the string will vibrate at many of its natural resonance frequencies at the same time. Exacly which resonance frequencies (and thus which mode shapes) make up the final string vibration depends on the shape of the initial string displacement. The movie at left (0.58MB mpeg) shows the vibration of a fixed-fixed string which has been plucked at a point 1/3 of its length from the left end (x = 1/3L). As you observe the vibration you should be able to visualize two wave pulses, one travelling clockwise, the other travelling counterclockwise. The time for one complete trip equals one period - if the string wave vibrating with a fundamental frequency of 440 Hz, then this vibration cycle would repeat itself 440 times per second. |
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