726 BELL SYSTEM TECHNICAL JOURNAL 



phonic studies of hearing; it includes such topics as the ear, the ampli- 

 fier, transmission, loudness, overloading and distortion. 



A third section, which discusses the electrical future for music, 

 will most intrigue the musician. After surveying the present state of 

 the art of pick-up, transmission, recording and reproduction of music, 

 the author visualizes some of the possibilities which might be most 

 immediately realized: reproduction in auditory perspective, electrical 

 music and electrical aids in teaching. 



To permit a rapid survey by the general reader, Mr. Mills has with- 

 drawn all tables and graphs from the main text and has grouped them, 

 with necessary explanations, at the end. This section forms a useful 

 compendium of numerical information on frequencies, decibels, 

 thresholds, response curves of microphones and loud speakers, loudness 

 and energy levels, masking and the like. 



The engineer will find "A Fugue in Cycles and Bels" interesting and 

 easy to read, and a source of data not always available, and he can 

 recommend it to those musicians whose serious interest in their art 

 leads them to delve into its physical basis. 



Influence of Experimental Technique on the Measurement of Differential 

 Intensity Sensitivity of the Ear} H. C. Montgomery. The lack of 

 agreement among previous measurements of differential intensity 

 sensitivity indicates that the values obtained depend to a large extent 

 on the experimental conditions. The relative importance of various 

 factors is indicated, and a procedure is suggested which was designed 

 to give the smallest possible values of differential intensity sensitivity. 

 Intensive measurements made by this method upon a single subject, 

 using a pure tone of 1000 cycles, gave values consistently smaller than 

 any previously reported. There is no sharp division between intensity 

 changes which can be perceived and those which cannot. The response 

 of the subject is essentially variable and can be described only by 

 statistical methods. 



Diurnal and Seasonal Variations in the Ionosphere During the Years 

 1933 and 1934.'' J. P. Schafer and W. M. Goodall. The most im- 

 portant results of daily ionospheric measurements made at Deal, 

 New Jersey, latitude 40° 15' N., longitude 74° 02' W., over the period 

 from March, 1933, to May, 1934, are given in this paper and may be 

 summarized as follows: 



1. There was a definite correlation between the noon value of 



ionic density of the Fi region and magnetic disturbances, a decrease in 



ionic density being obtained on magnetically disturbed days. 



« Jour. Acous. Soc. Amer., July, 1935. 

 ''Proc. I. R. E., June, 1935. 



