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Name: Alivia
Status: student
Grade: K-3
Location: OH
Country: N/A
Date: 8/10/2005


Question:
Why does a stick make that noise when you whip it through the air?


Replies:
Alivia,

EVERY sound is vibrations passing through the air. A vibrating rubber band, a vibrating speaker, clapped hands, all sound sources work by causing the air around them to vibrate. These air molecules, moving forward and backward, bang against other molecules. The vibration pattern travels through the air until it reaches your eardrum. This causes your eardrum to vibrate with the same pattern. Now you hear a sound.

If the vibrations are too infrequent (an extremely low pitch) your ear cannot hear it. This is what most moving sticks produce when they push the air around them. If the stick moves fast enough, the air around the stick gets a faster vibration, a pitch your ear can hear. In fact, the faster you move the stick, the higher the pitch you produce.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College


Very "simple" question!! Very complicated answer!! Whirling a stick through air the stick can vibrate in very complicated patterns depending upon its size, shape and its composition. In addition, the stick causes the air through which it moves to flow in very complicated ways, called "turbulent" flow. This sets up regions of high pressure and low pressure in surrounding air. When the pressure equalizes, sound is produced. A loud example is when a balloon "pops". The "rumble" you hear when a car is moving is another example.

Vince Calder



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