ABSTRACTS OF TECHNICAL PAPERS. 633 



simplest transition from one intensity to another. The source of 

 sound was a special moving coil telephone receiver having very little 

 distortion, actuated by alternating currents from vacuum tube oscil- 

 lators. Observations were made on twelve male observers. Average 

 curves show that at any frequency AEjE is practically constant for 

 intensities greater than 10^ times the threshold intensity; near the 

 auditory threshold AE/E increases. Weber's law holds above this 

 intensity, the value of AE/E = constant lying between 0.05 and 0.15, 

 depending on the frequency. As a function of frequency AE/E is a 

 minimum at about 2500 c.p.s., the minimum being more sharply 

 defined at low sound intensities than it is at high. This frequency 

 corresponds to the region of greatest absolute sensitivity of the ear. 

 Analytical expressions are given (Eqs. (2), (3), (4), and (5)) which 

 represent AE/E, within the error of observation, as a function of 

 frequency and intensity. Using these equations, it is calculated that 

 at about 1300 c.p.s. the ear can distinguish 370 separate tones between 

 the threshold of audition and the threshold of feeling. 



Use of the Noble Metals for Electrical Contacts} E. F. Kingsbury. 

 The paper describes the results of an investigation of the behavior of 

 gold, silver and the platinum metals as electrical contacts in com- 

 munication circuits. Platinum has heretofore been considered the 

 standard although some alloys of the platinum metals have been used 

 in especially severe conditions. The economic situation has, however, 

 encouraged the use of cheaper substitutes. Heretofore, accurate 

 knowledge has not been available concerning the intrinsic merit of 

 other materials. This problem is complicated by the various forms of 

 discharges and mechanical conditions encountered in practice. The 

 resistance, erosion, and transfer of contacts are discussed for a variety 

 of materials under various circuit conditions and in different atmos- 

 pheres. 



Economic Aspects of Engineering Applications of Statistical Methods.'^ 

 W. A. Shewhart. This note calls attention to possible applications 

 of modern mathematical statistical theory, to research, design, pro- 

 duction, inspection, supply, and other engineering problems. Atten- 

 tion is given to certain general types of problems in the solution of 

 which statistical applications have been made, and to the nature of 

 the possible economies effected thereby. It is reasonable to believe 

 that very definite economic advantages can be obtained in any large 

 industry through such applications. 



1 Technical Publication No. 95, A. I. M. M. E., March 1928. 



2 Journal of the Franklin Institute, Vol. 205, March 1928, pp. 395-405. 



