ENERGY DISTRIBUTION IN SPEECH 117 



In our judgment the most important of these data of speech study is 

 the actual energy distribution, considering speech as "a continuous Mow 

 of distributed energy, " in accorchmce with the ideas expressed in the 

 earlier paper. The present paper offers a determination of this 

 fundamental factor. 



To determine the energy distribution in speech to a high degree of 

 accuracy it would be desirable to analyze a certain amount of con- 

 nected speech and take a time average of the energy distribution of 

 the whole. This is not feasible at the present time, but a very close 

 approach to this result has been made. The method consists in 

 analyzing the speech waves as impressed on a condense transmitter, 

 using a tuned circuit to transmit narrow frequency bands of energy and 

 pronouncing the separate syllables of the connected speech so slowly 

 that the kick of a direct current galvanometer connected to an A. C. 

 thermocouple can be separately read for each syllable. Using a suit- 

 able calibration for the whole apparatus, the magnitude of this kick 

 can be interpreted in terms of the time integral of the energy at a 

 particular frequency setting for each syllable. A mean of the read- 

 ings for all the syllables in the "speech" at any frequency setting 

 gives the relative energy at that frequency. 



The present method is a modification of an earlier method in which 

 approximate analyses of speech sounds were made, using a condenser 

 transmitter, tuned circuit, an amplifying-rectifying circuit, and ballis- 

 tic -galvanometer. The method is, however, much improved as we 

 now have very accurately calibrated condenser transmitters of better 

 design,^ and a great deal of care has been taken to calibrate the suc- 

 cessive elements of the train of apparatus, and increase the resolving 

 power. 



Experimental Procedure 



Sound waves emitted from the mouth of the speaker are allowed to 

 fall upon the diaphragm of a condenser transmitter, connected in the 

 conventional manner to the input of a three-stage amplifier. The 

 output of this is impressed upon the input circuits of twin single 

 stage amplifiers, potentiometers being interposed to permit regula- 

 tion of the grid voltages of the twin amplifier tubes. 



The output circuits of the fourth stage consist of the high windings 

 of two step down ironclad transformers. These step down trans- 

 formers have a voltage ratio of 1 1 : 1 and are designed to work between 

 impedances of 6,000 and 50 ohms. The low^ impedance winding of 

 one of these transformers operates into a thermocouple heater of, 



' The present design of the condenser transmitter and its calibration are fully 

 treated in a paper by Dr. E. C. Wente which will appear shortly in this Journal. 



