Sound Blowing Out Candles
Name: Marliz C.
Date: Thursday, April 25, 2002
How can sound blow out a candle?
Sound is "waves" of air wiggling back and forth. It is the back-and-forth
wiggling that makes your ear drum vibrate. If you put your hand in front of
a loud low-pitched speaker, you can feel the vibrations. If a sound wave is
very loud, the air making up the wave moves back and forth a great deal.
For a candle, it is almost like being blown back and forth. This is what
puts out the flame.
Dr. Ken Mellendorf
Illinois Central College
Sound is moving oscillation of air from a region of pressure greater than
the ambient pressure and a region of pressure less than the ambient
pressure. If the frequency, and intensity of the sound is within a certain
range the air will oscillate with an amplitude sufficiently large that the
candle flame becomes mechanically unstable, or the low pressure is
sufficiently small that oxygen is depleted. In either case the candle will
extinguish. The ultimate example is if the air motion exceeds the speed of
sound and a shock wave results.
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Update: June 2012