368 VIBRATION OF PLATES 



Musical notes which are produced in different ways, 

 but have the same intensity and pitch, mostly differ in 

 quality, or character. If we strike any note on a piano, 

 and then sound the same note on a flute, an organ, or a 

 violin, or utter it with the voice, we shall notice a great 

 difference between the sounds. This difference in 

 ' quality ' or ' timbre,' or c character,' is partly due to faint 

 sounds which accompany the note, as, for instance, the 

 slight sound of rushing air which accompanies the blow- 

 ing of the flute, or to the circumstance that the note 

 struck may either rapidly decrease in intensity & 

 happens with the sounds of the piano, or it may main- 

 tain a uniform intensity as in the case of the organ. Bui 

 the main cause of the difference of character is the pro 

 duction of overtones, which accompany the fundamenta 

 tone ; these overtones not only differ in various soundin* 

 bodies, but differ even in the same body if it is soundec 

 in different ways. 



35. Vibration of Plates, Bells, Rods, and Air in tubes. - 

 Solid bodies of large surface compared with their thick 

 ness perform a variety of vibratory movements if sounde< 

 in different ways. Vibrating plates contain, instead c 

 the nodal points of a vibrating string, a succession of sue 

 points forming nodal lines. These nodal lines may b 

 made visible by covering the plate with fine sand befor 

 it is made to vibrate. As soon as the vibrations con. 

 mence, the sand leaves the vibrating parts, and accunu! 

 lates on the nodal lines. This beautiful mode of rendei 

 ing the vibrations of plates visible was suggested b; 

 Chladni, and the figures produced are hence usual! 

 termed Chladni's Figures. 



