162 Dr. E. Warburg on the Deadening of the Sounds 



tones are more strongly deadened by internal resistance than 

 deeper ones, nor of any investigation of the cause of this phe- 

 nomenon. 



The first part of this research contains experimental proofs of 

 the phenomenon in question, the second part an investigation 

 of the causes which produce it. 



Part I. 



When a bar of any material is connected with a solid source 

 of sound, sound-waves are transferred to it. If the duration of 

 the tones which the source of sound emits is adequate as com- 

 pared with the time within which the waves traverse the bar 

 (which is the case in the following experiments), direct and 

 reflected waves frequently pass through one another, and the bar 

 assumes a condition of stationary vibrations. The forward and 

 back waves, however, undergo a diminution of their amplitude in 

 consequence of the deadening forces which act upon the vibra- 

 ting particles ; and owing to this, the intensity of the motion of 

 sound in the bar diminishes with increasing distance from the 

 source of sound. 



Hence the author, in order to investigate the action of the 

 deadening forces of solids upon tones of varying heights, conducted 

 to the ear, through bars of various material, the sound of an in- 

 strument which simultaneously emitted tones of varying height; 

 the instrument in question was a musical box. It was before all 

 things necessary that the sound should reach the ear through 

 the conducting-rod only. The following method of insulation 

 was adopted with this view. 



A circular cylindrical bag of thin caoutchouc 250 millims. in 

 height, open above and filled to the top with water, was sus- 

 pended in a thick cylindrical glass vessel by drawing the edge 

 of the bag over the rim of the glass cylinder. 



When the musical box, protected by a caoutchouc case and sus- 

 pended by a thread, was sunk nearly to the bottom, the sound 

 could not at all be heard by a bystanding observer ; only by 

 holding a funnel close over the edge of the water could a few of 

 the highest notes be heard; these, however, were so feeble that 

 the height of the note could not be clearly distinguished. 



The sound of the box is powerfully imparted to the water, 

 which results, among other things, from the circumstance that, 

 when sunk in a glass vessel filled with water, it communicates a 

 powerful motion to the surrounding media through the inter- 

 vention of the water and the glass. The sides, too, of the bag are 

 set in powerful vibration ; for if the bag be freely suspended in the 

 air, a considerable amount of sound is imparted to it. As in this 

 case the free air, so also, when the caoutchouc bag is suspended in 



