3B30.10 - Speed of Sound in Air

Code Number:
3B30.10
Demo Title:
Speed of Sound in Air
Condition:
Good
Principle:
Wavelength of Sound in Air
Area of Study:
Acoustics

Disclaimer

Equipment:
Laptop computer, SoftScopeTM module, 2 microphones, meter stick or rod, clicker, Oscilloscope, Wavetech Wave Generator, Speaker, Microphone with good battery, Preamp. (Stereo microphone mixer), 2 meter stick, Camera and Power Supply.
Procedure:

Video Credti: Jonathan M. Sullivan-Wood

The speed of sound can also be easily shown with the SoftScopeTM module, a laptop computer, and a couple of microphones.  Usually we space the two microphones at 50 cm, and set the SoftScope for single trigger.  Use the clicker to trigger and the measurements off the computer screen to calculate the speed of sound.

Assemble the apparatus as shown.  With the microphone in one channel and the wave generator in another you will get a measurable wave shift on the oscilloscope. From this you can directly measure the wavelength using the meter stick, and determine the speed by knowing the frequency as read on the digital wave generator or oscilloscope.  The meter stick is used to measure the distance between the speaker and the microphone.  Using higher frequencies (660 Hz, 990 Hz, etc.) you can cut out some of the background interferences as the microphone and speaker will be closer together for 1 complete shift of wavelength.

References:
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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.