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DELL SYSTEM TECHNICAL JOURNAL 



below 1000 cycles per second has a syllable articulation of 40 per 

 cent. Similarly on the curve labelled "Articulation H" the point 

 (1000, 86) means that a system which transmits only frequencies 

 above 1000 cycles per second has a syllable articulation of 86 per 

 cent. The dotted curves show the per cent of the total speech energy 

 which is transmitted through the filter systems used in the articula- 

 tion tests. These curves are derived from the results of Crandall 

 and MacKenzie which were recently published.^ 



It will be seen that although the fundamental cord tones with 

 their f^.rst few harmonies carry a large portion of the speech energy, 



Effect upon the Articulation and the Energy of Speech 

 of Eliminating Certain Frequency Regions 



1000 



2000 3000 



Freguency 



Fig. 8. 



moo 



they carry practically none of the speech articulation. A filter 

 system which eliminates all frequencies below 500 cycles per second 

 eliminates 60 per cent of the energy in speech, but only reduces the 

 articulation 2 per cent. A system which eliminates frequencies 

 above 1500 cycles per second eliminates only 10 per cent of the speech 

 energy, but reduces the articulation 35 per cent. A system which 

 eliminates all frequencies above 3000 cycles per second has as low a 

 value for the articulation as one which eliminates all frequencies 

 below 1000 cycles per second. This last statement may appear 

 rather astonishing since it is contrary to the popular notion of the 

 relative importance of various voice frequencies from an interpre- 

 tation standpoint. 



The two solid curves intersect on the 1550 cycle abscissa and at 

 65 per cent articulation, which shows that using only frequencies 



* See preceding paper. 



