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Name: Rue
Status: educator
Grade: 6-8
Location: NC
Country: USA
Date: Fall 2011


Question:
When studying percussion instruments, students discovered: (a) the sound of metallophone bars (metal bars similar to a vibraphone) is sustained and (b) the sound of xylophone bars (wooden bars) is not sustained. Students wanted to know why the metal bars have a "longer sound" than the wooden bars.

Replies:
Rue,

Metal is more elastic than wood. Consider a hard metal rod and a hard wooden rod of the same shape and size. Bend each one a little and the metal rod is more likely to go back to its original shape. For the wooded bar, tiny bits and pieces of the wood structure are damaged every time the bar bends. This uses up the vibration energy quickly.

Dr. Ken Mellendorf Physics Instructor Illinois Central College


Because metals are very solid they transmit sound quickly and efficiently. Wood on the other hand has air pockets and individual fibers that move around and absorb energy very well as sound passes. The wood eats up the energy of the strike in a thing called internal resistance.

Hit one end of a 2X4 and the sound dies out over the length of the wood. Sound can be heard in rail road rails over many miles.

R.W. "Mr. A." Avakian Instructor Arts and Sciences/LRC Oklahoma State Univ. Inst. of Technology


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