Abstracts of Technical Articles from Bell System Sources 



Stability of Two-Meter Waves} Charles R. Burrows, A. Decino 

 and LoYD E. Hunt. The continuous records of the field strength 

 received over a 60-kiIometer path on a frequency of 150 megacycles 

 for the year 1936 are analyzed. Preliminary comparison with other 

 paths of the same length indicate that the magnitude of the recorded 

 variations of the signals may be typical of paths of this length. 



A reduction in the path length by a factor of two reduced the 

 fading range in decibels by a factor of five. 



The results are found to be in agreement with an earlier formula. 

 Fading reduced the field 7 decibels below the average value 1 per cent 

 of the time. 



Loudness, Masking and Their Relation to the Hearing Process and 

 the Problem of Noise Measurement} Harvey Fletcher. It is shown 

 in this paper how to define loudness and loudness level in a quantitative 

 way. Definite procedures are given for determining experimentally 

 the loudness level of any sound heard by any person. For a typical 

 observer a true loudness scale is developed. The relation of the scale 

 to the loudness level scale is determined experimentally. The scale 

 has been found to be very useful for calculating loudness from the 

 noise spectrogram, the noise audiogram, or the overtone structure of 

 the sound. 



The relation between the masking and the loudness produced by 

 a sound has been quantitatively determined and a formula deduced 

 from this relation which has proved useful for calculating the loud- 

 ness. This formula may be applied with equal success to a normal 

 ear and also to a deafened ear. Evidence has been given that the 

 masking expressed in decibels produced upon any pure tone is equal 

 directly to the agitation of 1.1 per cent of the total nerve endings 

 expressed in decibels above the threshold value for such a patch and 

 at the position where such a tone would be sensed. These loudness 

 relations throw light upon some of the important processes involved 

 in hearing. In particular the data from the masking effects of thermal 

 noise were used to calculate the relation between the position of 



1 Proc. I. R. E., May 1938. 



2 Jour. Acous. Soc. Amer., April 1938. 



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