3B35.30 - Parabolic Reflector and Sound Source | Instructional Resources and Lecture Demonstrations

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

Disclaimer

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.

^{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.}