3B35.30 - Parabolic Reflector and Sound Source

The reflectors can be used in two ways.  The best is to put a speaker at the focal point of a reflector, and pointing in at the reflector.  Use a tape player to play music or speech through the speaker, and "beam" the signal to the students in the audience. The other way to use these is in the original way they were designed.  That is to directionally listen to sound from far away using the parabolic reflector with built in microphone. See 2nd paragraph procedure.
Code Number:
3B35.30
Demo Title:
Parabolic Reflector and Sound Source
Condition:
Excellent
Principle:
Acoustic Reflectors
Area of Study:
Acoustics
Equipment:
Parabolic reflectors, tape player, speaker, headphones, amplifier.
Procedure:

The reflectors can be used in two ways.  The best is to put a speaker at the focal point of a reflector, and pointing in at the reflector.  Use a tape player to play music or speech through the speaker, and "beam" the signal to the students in the audience. 

The other way to use these is in the original way they were designed.  That is to directionally listen to sound from far away using the parabolic reflector with built in microphone.  However, in the classroom, you are only able to do this with the headphones on, which means that only one student at a time is able to experience the effect.  If you hook the parabolic reflector with microphone to an amplifier and speaker, you will start to get uncontrollable feedback, mostly due to the reflection off the classroom walls of the signal you are amplifying.

 

References:
  • Charles Vivian, "How to Reflect Sound", Science Experiments & Amusements For Children, p. 38.
  • David Kutliroff, "4, Producing a Beam of Sound", 101 Classroom Demonstrations and Experiments For Physics Teachers, p. 25.
  • Vicki Cobb and Kathy Darling, "Sound Advice", Bet You Can!, p. 50.
  • Spion™, Electronic Listening and Digital Recording Device, Instruction Manual.

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