264 



The Symballophone 



scope. While clinical observations were being made, experimental studies were 

 begun to determine the most effective device for enhancing the illusion pro- 

 duced by the use of tubes of varying length and bore. 



Through the cooperation of Professor C. W. Brown of the Department of 

 Psychology, University of California, the studies which will be described were 

 made. By means of a gravity-pressure system, water was caused to flow through 

 rubber tubing arranged in such a way that the flow could be impeded by metal 



R«p7»ee«nt arcentpic pump. 



Fig. 5. — A device for the study of the capacity of the two ears to detect differ- 

 ences in intensity and timing of sounds with the symballophone. Water under 

 hydrostatic pressure was allowed to flow through the system of tubing at A or B. 

 An eccentric pimip E gave an impetus to the current to represent the pulse wave 

 and to accentuate the sounds produced by faults in streamlining at points 

 ^1,2,3,4 gj^jj g 1,2, 3, 4 Metal cylinders of different bore were placed in the rubber 

 tubing at points A^' -• *■ * equidistant from the point of inflow, and metal cylinders 

 of equal bore were placed at points B^--^* at varying distances from the point 

 of inflow. For comparison of sounds the two chest pieces of the symballophone 

 were placed over the two obstructions where sounds were to be compared. In this 

 manner differences in intensity of soimd were studied over A^-'''* and differences 

 of timing over B.^-'^'* 



cylinders with bores (1) of varying diameters or (2) of equal diameter but so 

 placed that they were at unequal distances from the point of inflow. The 

 vibrations caused by the water passing through these narrowed apertures, 

 which could be heard as sounds (murmurs), were studied with the aid of the 

 symballophone. An eccentric pump was inserted in the pressure system above 

 the obstructions to simulate the pulse wave and to enhance the sounds (mur- 

 murs). Figure 5 shows the details of the arrangement.* 



Soon it was apparent that the ears are so sensitive that extremely small dif- 

 ferences in intensity or time could be readily detected by untrained persons 



* Throughout this study I had the assistance of two able senior medical students, A. M. 

 Bassett and M. J. Goldman, to whom I am greatly indebted. 



