432 



GENERAL SCIENCE 



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MUSIC- YANKEE DOODLE 

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FIG. 322. A section of a music roll for a player piano. 



Courtesy of the Autopiano Company. 



Phonograph. Whenever a needle or sharp instrument is at- 

 tached to a disc and sound waves strike the disc or diaphragm, 

 the disc will vibrate, causing the needle also to vibrate. If the 

 point of the needle is drawn along over some soft material, the 

 vibrating needle will leave impressions in the substance. This 

 is exactly what happens when a record is made for a phonograph. 

 If a person sings into the large end of a horn, the sound waves will 

 be collected at the small end. If a disc is placed at the small end 

 of the horn and a needle is attached to the disc, the disc will vi- 

 brate, causing the needle to vibrate and cut grooves in any soft 

 substance. When the soft material is moved along at uniform 

 rate the sound waves will be recorded. 



Now, if a needle, to which is attached a disc or diaphragm, 

 is allowed to run in the little grooves which have been made on 

 the wax, a sound will be produced like the sound of the voice 

 wnich spoke in the horn. Since this wax is too soft to retain its 



