THE GRAMOPHONE REDDIE. 



229 



Pig. 21. — Gong : 0.4 second. 



The first practical talking machine working on this principle was 

 made by Mr. Short, who patented his invention in 1898. The Hon. 

 C. A. Parsons then took up the invention, and considerably improved 

 it. I have a model here of the improved Parsons sound box (fig. 19). 

 The auxetophone sound box as used to-day is on substantially the 

 same lines, though its construction has been simplified. 



Before closing this paper I should like to give you some details 

 concerning the sound line in a gramophone record, and show you 

 some magnified trac- 

 ings of sound waves. 

 The approximate 

 length of the spiral 

 line in a fully recorded 

 12-inch record, carry- 

 ing the sound line to 

 within 2^ inches of its 

 center, is tt times 

 the mean diameter 

 multiplied by the num- 

 ber of turns — that is, 

 •n- X 8 X 350 inches = 244 yards 1 foot. But this is the length of the 

 line without the ripples. These at least double its length, if the pitch 

 of the record is high and the sounds recorded rich in harmonics, so 

 that we have a sound line over 480 yards long. It is no wonder that 

 the needle point must be finely tempered, and that it shows signs of 

 wear after playing a record. Its average speed over the record is 

 31.8 inches per second. For a fundamental note on middle C, this 



gives us about 

 8 vibrations per 

 inch. 



The tracings 

 which I have here 

 are some made by 

 Professor Scrip- 

 ture of Washing- 

 ton, and are reproduced in his interesting work. Researches in Experi- 

 hiental Phonetics. They are traced by a specially constructed instru- 

 ment from actual gramophone records, and they show the sound line 

 on a very much magnified scale. 



The " time equation " of the tracings shown by, Professor Scripture 

 is 1 millimeter = 0.0004 second — that is to say, 1 millimeter length of 

 the tracings shows the sound waves produced in 0.0004 of a second, or 

 8.2 feet per second. The reproductions shown in the figures are about 

 half full size, so that 4.1 feet equals the length of tracing for 1 second. 



Fig. 22. — Piano and whistle : 0.1 second. 



Pig. 23. — Plucked string : O.O.". second. 



