Resources: Sound's Cool! - Exploring Sound Waves

• Energy and Its Transformations: Sound - FCPS Promotion Benchmark 11 Lesson Review
• A Vernier microphone connected to a LabPro interface and Logger Pro software was used to capture an experimental recording of the waveform of a 512-cycle tuning fork. [From the menubar, select Analyze/Autoscale Graph/Autoscale (Button Default); "stretch" x-axis until waveform is clearly visible (move cursor over x-axis; click & drag); click arrows along time scale in order to scroll graph left & right.]
• "Audacity," the free, cross-platform audio editor. Use sample sound files to demonstrate the following points-of-focus:
  1. change in amplitude = change in volume;
  2. change in frequency = change in pitch;
  3. noise cancellation (destructive interference) and phasing (constructive & destructive interference).
• Activity questions:
  1. Ultrasound: see medical ultrasound imagery (PSLG p. 72, "Application" question No. 2, "Medical ultrasound")
  2. SONAR (PSLG p. 72, "Application" question No. 2, "Sonar")
  3. Echolocation (PSLG p. 72, "Application" question No. 2, "Echolocation")
  4. Noise Cancellation: "Noise cancellation equipment uses a microphone to pick up sound waves from a noise source. The microphone's output is fed to a computerized signal processor, which generates a waveform identical to the original--but 180 degrees out-of-phase. This out-of-phase signal is amplified and directed back toward the noise source via a speaker system. When the two sound waves combine, they cancel out each other, reducing the noise." See also, How Sound Waves Interact with Each Other (constructive & destructive interference), and How Noise-Cancelling Headphones Work (PSLG p. 73, "Application" question No. 3, "noise cancelling headphones").
  5. Speed of light- versus sound waves: Questions and Answers About Lightning; see "Flash-to-Bang" (PSLG p. 74, "Application" question No. 6, "Explain why you see lightning before you hear thunder.") [Note: speed of sound at sea level = 340.29 m/s; the speed of light = ~300,000,000 m/s (299,792,458 m/s). Light travels ~1,000,000 times faster than sound.]
• Post-lab demostrations:
  1. speaker/microphone [analogous to a motor/generator: a speaker is powered by electricity, causing an electromagnetic coil of wire to move inside a permanent magnet (similar to a motor); a microphone induces an electric current by moving a coil of wire inside a permanent magnet (similar to a generator)]
     1. How A Speaker Works (Java applet)
     2. Dynamic Microphones. See also, Dynamic microphones.
  2. Doppler effect (demo using a tuning fork tied securely to a length of string). Applications:
     1. National Weather Service Doppler RADAR (follow the sidebar hyperlink to 4. Radar Images; see the section entitled, "Velocity Images")
     2. Police RADAR, LIDAR, and LASER devices:
        1. Friday, 13 April 2007, Pfc. Marvin Goodley, School Resource Officer, FCPD, demonstrated how Kustom police RADAR- and LIDAR devices use light and sound to measure speed and distance (a Microsoft Office PowerPoint presentation by Phil Wherry). Enrichment: See Police RADAR for a quantitative look at the Doppler effect. See also, LIDAR Tutorial (NASA).
        2. Tuesday, 25 March 2008, FCPD Officers Cicinato and Goodley teamed up to demonstrate police RADAR and LIDAR. Mr. Phillip Wherry demonstrated the Mattel® Hot Wheels® RADAR Gun, a $30 consumer-grade device that works remarkably well despite its limited range of 12 meters (39 feet)!
        3. Wednesday, 11 March 2009, FCPD Officers Buckhaults, Cicinato, and Ziants provided an extraordinary opportunity for select Sandburg MS Physical Science students to operate the following police RADAR and LIDAR devices by Kustom Signals, Inc.: ProLaser® III [LIDAR (laser light)]; Pro-Lite+ [LIDAR (laser light)]; Talon II (RADAR); and Laser Labs, Inc. Model 100 Tint Meter (LASER). Police RADAR and LIDAR devices were used like a JUGS sports radar gun to measure the speed of students running (~12-17 mph).
• Enrichment: Use an audio editor (like a word processor for spoken language, sounds & sound effects, etc.) -- such as "Audacity" -- to create an audio recording (a "podcast") that exemplifies one or more points of focus from the FCPS lab activity, Sounds Cool! Audacity help files: Documentation and Support (see also, Documentation); Audacity Tutorial: How to Record and Edit Audio with Audacity; Creating a simple voice and music Podcast with Audacity.