ABSTRACTS OF TECHNICAL PAPERS 547 



Modern Developments in Inspection Methods.^ E. D. Hall. This 

 extensively illustrated article describes inspection methods as carried 

 out at the Hawthorne plant of the Western Electric Company. The 

 number of individual piece parts manufactured is more than 100,000 

 and the number of inspection gauges employed totals more than 25,000. 

 Machine testing and gauging for certain parts is described and cost 

 savings resulting therefrom are given. One of the machines described 

 tests a porcelain protector block containing a carbon insert. The 

 machine is adjusted to accept blocks from which the recess distance 

 of the carbon lies between 0.0024 and 0.0032 inch and to reject, 

 when the distance is 0.0023 inch or less or 0.0033 inch or more. 

 The machine performs its operation at the rate of 2,800 blocks per 

 hour. It is used to test about 4,500,000 blocks per year and repre- 

 sents an annual saving of approximately $2,500. 



A Direct Comparison of the Loudness of Pure Tones. ^ B. A. Kings- 

 bury. The loudness of eleven pure tones was studied by adjusting 

 the voltage applied to a telephone receiver to make these tones as 

 loud as certain fixed levels of a 700-cycle tone. The average results of 

 22 observers, 11 men and 11 women, were arranged as contour lines 

 of equal loudness through the normal auditory sensation area in terms 

 of r.m.s. pressure in car canal as a function of frequency. Frequencies 

 from 60 to 4,000 cycles were used and intensities from threshold of 

 audibility to 90 T. U. above the 700-cycle threshold. It was found 

 that if the amplitudes of pure tones are increased in equal ratios the 

 loudness of low frequency tones increases much more more rapidly 

 than that of high frequency tones. For frequencies above 700 cycles 

 the rate is nearly uniform. 



As a loudness unit the least perceptible increment of loudness of a 

 1,000-cycle tone was employed. In absolute magnitude this varies 

 from level to level, but in the ordinary range of loudness it becomes 

 constant. This unit takes into account the subjective character of 

 loudness. 



The variability of the data from which the averages were computed 

 was separated into a factor expressing dissimilarity of ears and another 

 expressing errors of observers' judgment. There was no level at 

 which the variances were a minimum. Dissimilarity of ears causes 

 more variation than errors of observers' judgment. The variances 

 showed no significant sex difference. 



■* Mechanical Engineering, Vol. 48, p. 1435, 1926. 

 ^Physical Review, Vol. 29, p. 588, 1927. 



