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Code Number: 3B30.61
Demo Title: Speed of Sound in a Rod
Condition: Excellent
Principle: Wavelength of Sound in Solids
Area of Study: Oscillations & Acoustics
Equipment:
Digital Oscilloscope, 2 Microphones, Iron, Brass, Aluminum Rods, and Short Striker Rod.
Procedure:
The speed of sound in solids can also be easily shown with the digital oscilloscope, 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 oscilloscope for single trigger. This is automatic if you bring up the "stored" setting on the oscilloscope. 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.
References:
- 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.
- Harald C. Jensen, "The Velocity of Sound in Metals", AJP, Vol. 23, #4, Apr. 1955, p. 246.
Video Credit: Jonathan M. Sullivan-Wood