3B30.61 - Speed of Sound in a Rod

Code Number:
Demo Title:
Speed of Sound in a Rod
Wavelength of Sound in Solids
Area of Study:
Laptop Computer, SoftScopeTM Module, 2 Microphones, Iron, Brass, Aluminum Rods, and Short Striker Rod.

Video Credit: Jonathan M. Sullivan-Wood

The speed of sound in solids can also be easily shown with the SoftScopeTM module, a laptop computer, and a couple of microphones connected to various metal rods.  In our case, we use brass, iron, and aluminum rods.  Usually we space the two microphones at 50 cm, and set the SoftScope for single trigger.  Use the striker rod to trigger and the measurements off the computer screen to calculate the speed of sound.  Either transverse or longitudinal speeds can be shown.  Striking the rod on the end will give the speed for longitudinal waves.  Striking the rod on the side but towards one end will give the speed for transverse waves.  These speeds will be different.

  • Michael Hirth, Sebastian Gröber, Jochen Kuhn, and Andreas Müller, "Harmonic Resonances in Metal Rods – Easy Experimentation with a Smartphone and Tablet PC", TPT, Vol. 54, #3, Mar. 2016, p. 162.
  • Earl D. Blodgett, "Comments on 'Speed of Sound in Metal Pipes: An Inexpensive Lab'", TPT, Vol. 47, #1, Jan. 2009, p. 31.
  • Elisha Huggins, "Speed of Sound in Metal Pipes: An Inexpensive Lab", TPT, Vol. 46, #1, Jan. 2008, p. 13.
  • David Potter, "The Speed of Sound in an Iron Rod", TPT, Vol. 40, #1, Jan. 2002, p. 56.
  • Tony Key, Robert Smidrovskis, and Milton From, "Measuring the Speed of Sound in a Solid", TPT, Vol. 38, #2, Feb. 2000, p. 76.
  • Michael T. Frank and Edward Kluk, "Velocity of Sound in Solid", TPT, Vol. 29, #4, Apr. 1991, p. 246.
  • Gerald P. Hart, "Measurement of the Speed of Sound in Metal Rods Using the Microcomputer", TPT, Vol. 24, #2, Feb. 1986, p. 89.
  • Thomas B. Greenslade Jr., "19th Century Textbook Illustrations XXVIII: The Ringing Bar", TPT, Vol. 17, #1, Jan. 1979, p. 44.
  • S. Velasco, F. L. Román, and J. A. White, "A Simple Experiment for Measuring Bar Longitudinal and Flexural Vibration Frequencies", AJP, Vol. 78, #12, Dec. 2010, p. 1429.
  • Nobuo Naba, "Observation of Longitudinal Vibration of Metal Rods", AJP, Vol. 40, #9, Sept. 1972, p. 1339.
  • Charles R. Rhyner, "Measurement of the Speed of Sound in Metal Rods", AJP, Vol. 38, #9, Sep. 1970, p. 1152.
  • Oakes Ames, "A Direct Measurement of the Speed of Sound in Rods", AJP, Vol. 38, #9, Sep. 1970, p. 1151.

Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.