3B35.10 - Gas Lens

Code Number:
Demo Title:
Gas Lens
Focusing sound, gas lens
Area of Study:
Balloons, gases that are lighter or heavier than air.

Fill the balloon with air or some other gas.  Hold the balloon close to your ear and you should be able to find a spot where the balloon acts like a lens and focuses the sound.  Gases of different densities will give some interesting effects to the focused sound.

  • Pietro Ferraro, "Optics with Balloons", TPT, Vol. 34, # 5, May 1996, p. 274.
  • T. R. Sandin, "Viscosity Won't Curve It", TPT, Vol. 24, # 2, Feb. 1986, p. 70.
  • Thomas B. Greenslade, Jr., "The Acoustic Lens", TPT, Vol. 16, # 2, p. 100, Feb. 1978
  • Richard Reis, "A Sound Lens", TPT, Vol. 6, # 1, Jan. 1968, p. 40.
  • Daniel A. Russell, "Basketballs As Spherical Acoustic Cavities", AJP, Vol. 78, # 6, June 2010, p. 549.
  • Derek C. Thomas, Kent L. Gee, R. Steven Turley, "A Balloon Lens: Acoustic Scattering From a Penetrable Sphere", AJP, Vol. 77, # 3, p. 197, March 2009.
  • George M. Hopkins, "Refraction of Sound", Experimental Science, p. 164.

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