RECORDING AND REPRODUCING OF MUSIC AND SPEECH 513 



Such a method has Ijeen developed which at the present time covers a 

 range of frecjuencies from somewhere below 50 to about 4,500 pps. 

 Work is still being continued to extend the method to the higher 

 frequencies. This method of measurement has been^very useful not 



Mi,lr,-5ccr/on 



Fig. 13 — Electromagnetic recorder using lumped loaded termination 

 The method of furnishing dissipation to the lumped loaded line is shown 



only in determining the magnitudes of the impedances in the degrees 

 of freedom in which it is desired that they shall operate, but in deter- 

 mining the impedances to motion of the various parts in directions 

 in which they should not be permitted to vibrate. In connection 

 with the measurement of the magnitudes of the parts in the desired 

 degrees of freedom this method enables us to determine the constants 

 of the mechanical networks under their conditions of operation. 

 Experience so far has indicated that when all the degrees of freedom 

 have been taken into account and when the dynamic axes of vibration 

 have been properly chosen, the static and dynamic constants of the 

 parts are the same, and it is then possible to check the parts by simple 

 static measurements. In the early attempts to build these systems 

 very large discrepancies between the static and dynamic character- 

 istics were found. 



