Abstracts of Technical Articles from Bell System Sources 



What Electrons Can Tell Us about Metals} C. J. Davisson. Some 

 general statements are made about electron waves and electron 

 diffraction, three typical investigations in which electron diffraction 

 has been employed are described, and the technique of a new type of 

 electron crystal analysis is discussed. 



Relation between Loudness and Masking} Harvey Fletcher and 

 W. A. MuNSON. A functional relationship between the loudness of a 

 sound and the degree to which it masks single frequency tones, that is, 

 the masking audiogram of the sound, is developed. A loudness- 

 masking function is determined experimentally. From tlris loudness- 

 masking relationship the loudness of a sound can be computed by 

 simply integrating the area under the masking audiogram plotted on a 

 special chart. Comparisons of computed and observed loudness 

 levels are shown for a number of sounds and serve to illustrate the 

 precision to be expected from the method. Finally, the results of a 

 large number of masking tests are given in the form of masking con- 

 tours, which enable one to predict the masking audiogram of a sound 

 from measurements of its intensity spectrum. 



Coupling between Parallel Earth-Return Circuits under D.-C. Tran- 

 sient Conditions} K. E. Gould. In tests conducted in connection 

 with several d.-c. railway electrifications, the induced voltages re- 

 corded in paralleling communication circuits at times of short circuit 

 on the railway have shown marked divergences from values computed 

 on the basis of uniform earth resistivity and a rate of change of earth 

 current determined from measurements in trolley and rail circuits. 

 Due to the numerous factors which might contribute to these divergen- 

 ces, such as non-uniform division of transient current along the tracks 

 and associated return conductors, the presence of shielding conductors 

 along or near the right-of-way, etc., it was felt that a better under- 

 standing of the problem of induction under d.-c. transient conditions 

 could be obtained by experimental studies of the transient coupling 

 between parallel earth-return circuits, free from the effects of shielding 

 conductors, and with concentrated, rather than distributed, grounds. 

 The study described in this paper was undertaken for this purpose. 



1 Jour, of Applied Physics, June 1937. 

 ^ Jour. Acous. Soc. Amer., July 1937. 

 ^ Electrical Engineering, September 1937. 



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