Abstracts of Technical Articles from Bell System Sources 



A Space-Time Pattern Theory of Hearing} Harvey Fletcher. 

 The pitch of a tone is determined both by the position of its maximum 

 stimulation on the basilar membrane and also by the time pattern 

 sent to the brain. The former is probably more important for the 

 high tones and the latter for the low tones. The loudness is dependent 

 upon the number of nerve impulses per second reaching the brain and 

 possibly somewhat upon the extent of the stimulated patch. The 

 experience called by psychologists "volume" or "extension" is no 

 doubt identified with the length of the stimulated patch on the basilar 

 membrane. This extension is carried to the brain and forms a por- 

 tion of excited brain matter of a definite size. It is then this size that 

 determines our sensation of the "volume" of a tone. The low pitched 

 or complex tones have a large "volume" while the high pitched tones 

 have a small one. 



The psychological experience called "brightness" may be identified 

 with the sharpness of the peaks in the vibration form of the basilar 

 membrane as suggested by Dr. Troland. The high tones give the 

 sense of brightness while the low tones the sense of dullness. 



The time pattern in the air is converted into a space pattern on the 

 basilar membrane. The nerve endings are excited in such a way that 

 this space pattern is transferred to the brain and produces two similar 

 space patterns in the brain, one on the left and the other on the right 

 side. Enough of the time pattern in the air is sent to each of these 

 stimulated patches to make times of maximum stimulation in each 

 patch detectable. So when listening to a sound with both ears, there 

 are four space patterns in the brain produced, each carrying also some 

 sort of time pattern. It is a recognition of the changes in these pat- 

 terns that accounts for all the phenomena of audition. 



The Theory of Probability: Some Comments on Laplace's Theorie 

 Analytique? E. C. Molina. This paper is concerned with an answer 

 to the questions "to what extent will one conversant with the Theorie 

 Analytique be in touch with the present status of probability theory, 

 and how sound a foundation will he have found therein for statistical 

 applications of the theory?" 



^Jour. Aeons. Soc. Amer., April, 1930. 

 '^Bulletin, Amer. Math. Soc, June, 1930. 



836 



