3B55.10 - Interference of Sound Waves - Rotating Platform, LED

Code Number:
3B55.10
Demo Title:
Interference of Sound Waves - Rotating Platform, LED
Condition:
Good
Principle:
Constructive & Destructive Interference of Sound Waves
Area of Study:
Acoustics
Equipment:
2 large speakers, amplifier, wave generator, and LED mounted with Microphone.
Procedure:

Mount the two speakers on a moveable table so that the tweeters are 1 meter apart.  The wave generator should be run at 1000 Hertz or more.  LR 70 works best for this as it is a square room and therefore easy to set up a standing wave pattern.  When the pattern is produced the students should be able to move their heads from side to side and detect the standing wave pattern.

The LED mounted with the microphone is so that you can show where the nodal points are in a room, (The LED will light at the peaks and go out at the nodes).

References:
  • Chris Chiaverina, "Performing Acoustic Experiments Using Inexpensive Bluetooth Speakers and Smartphone Signal Generator Applications", TPT, Vol. 60, #2, Feb. 2022, p. 152.
  • Kenneth W. Trantham and L. Janssen, "Multiple Source Interference with Sound", TPT, Vol. 57, #8, Nov. 2019, p. 555.
  • Robert D. Polak, Nicolette Fudala, Jason T. Rothchild, Sam E. Weiss, and Marcin Zelek, "Easily Accessible Experiments Demonstrating Interference", TPT, Vol. 54, #2, Feb. 2016, p. 120. 
  • Roberto Machorro and E.C. Samano, "How Does it Sound? Young Interferometry Using Sound Waves", TPT, Vol. 46, #7, Oct. 2008, p. 410.
  • James Strachan, "Destructive Interference Between Computer Speakers", TPT, Vol. 44, #7, Oct. 2006, p. 473.
  • Burt Brody,  "Destructive Interference with a Circular Saw Blade", TPT, Vol. 40, #4, Apr. 2002, p. 250.
  • Thomas B. Greenslade and Joshua A. Mason, "Ultrasonic Interferometers", TPT, Vol. 36, #4, Apr. 1998, p. 249.
  • John D. McGervey,  "Hands-on Physics for Less Than a Dollar per Hand-Part III", TPT, Vol. 34, #7, Oct. 1996, p. 448.
  • Robert M. Williamson, "Some Standing Waves Aren't Quantized", TPT, Vol. 34, #6, Sept. 1996, p. 326.
  • Nilgun Sungar, "Teaching the Superposition of Waves", TPT, Vol. 34, #4, Apr. 1996, p. 236.
  • Thomas B. Greenslade, "Experiments with Ultrasonic Transducers", TPT, Vol. 32, #7, Oct. 1994, p. 392.
  • Robert G. Hunt, "Dancing to a Different Tune", TPT, Vol. 31, #4, Apr. 1993, p. 206.
  • John E. Peterson, "A Low-Cost Audio Oscillator", TPT, Vol. 16, #5, May 1978, p. 303.
  • Thomas B. Greenslade, Jr., "The Acoustic Lens", TPT, Vol. 16, #2, Feb. 1978, p. 100.
  • Robert W. Schramm, "Using a Stereo Tape Recorder as a Demonstration Device", TPT, Vol. 12, #3, Mar. 1974, p. 172.
  • Mario Iona, "Error Analysis", TPT, Vol. 9, #2, Feb. 1971, p. 62.
  • M. H. Teller, "Wave Interference, Using Transducers", TPT, Vol. 8, #5, May 1970, p. 259.
  • David P. Koch, "Two -Source Interference Transparency", TPT, Vol. 7, #2, Feb. 1969, p. 103.
  • Lester Dwyer, "Demonstrations of Reflection and Diffraction of Sound", TPT Vol. 6, #5, May 1968, p. 252, also A Potpourri of Physics Teaching Ideas - Sound, p. 250.
  • Ralph Baierlein and Vacek Miglus, "Illustrating Double-Slit Interference: Yet Another Way", AJP, Vol. 59, #9, Sept. 1991, p. 857.
  • W. N. Mathews Jr., "Superposition and Energy Conservation for Small Amplitude Mechanical Waves", AJP, Vol. 54, #3, Mar. 1986, p. 233.
  • James Thornton, "A Technique for Sound-Wave Visualization", AJP, Vol. 52, #5, May 1984, p. 465.
  • Haywood Blum, "Acoustic Interference Demonstration", AJP, Vol. 42, #5, May 1974, p. 413.
  • G. D. Freier and F. J. Anderson, "Sl-3. Interference of Sound Waves", A Demonstration Handbook for Physics.
  • G. D. Freier and F. J. Anderson, "Sl-2. Phase and Group Velocity", A Demonstration Handbook for Physics.
  • "W-320. Corrugated Roofing & Sew. Tape", DICK and RAE Physics Demo Notebook.
  • "W-330. Two Speakers - Aluminum Rod", DICK and RAE Physics Demo Notebook.
  • Robert Ehrlich, "Q.7. Beeper at the Center of a Hollow Tube", Turning the World Inside Out, p. 199 - 200.
  • Jearl Walker, "3.17. Reflection Tone", The Flying Circus of Physics Ed. 2, p. 152.
  • Yaakov Kraftmakher, "1.2, Interference of Sound Waves", Experiments and Demonstrations in Physics, ISBN 981-256-602-3, p. 12 - 14.
  • Christopher P. Jargodzki and Franklin Potter, "168, Where Does the Energy Go?", Mad About Physics, p. 62, 206.
  • James Cunningham and Norman Herr, "Interference of Sound", Hands-on Physics Activities with Real Life Applications, p. 425 - 426, 430 - 431.
  • W. Bolton, "Interference With Sound (1)", Book 2 - Waves and Particles, Physics Experiments and Projects, 1968, p. 59 - 60.




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.