ARTICULATION MEASUREMENTS 277 



are plotted on a graph with the hearing loss in decibels as the ordinates and 

 the frequency as the abscissa. 



11.12. Articulation Measurements ■*''• ^s. — In the case of speech trans- 

 mission the primary object is the realization of conditions which will result 

 in the maximum intelligibility. Intelligibility is used to signify the 

 accuracy and ease with which the articulated sounds of speech are rec- 

 ognized. 



Many methods and tests are used to determine the person's ability to 

 recognize the sounds of speech. Fundamentally, these methods consist 

 of pronouncing speech sounds into one end of a transmission system and 

 having the observer write the sounds which are heard at the receiving end. 

 The comparison of the called sounds with those observed shows the 

 number and kind of errors which are made. The system may be the air 

 between the mouth and the ear in a room or it may be a telephone system, 

 or a sound reproducing system such as a phonograph, radio or sound 

 motion picture. 



Speech material of various kinds may be used. The percentage of the 

 total number of speech sounds which are correctly observed is called the 

 sound articulation. The terms vowel articulation and consonant articu- 

 lation refer to the percentages of the total number of spoken vowels or 

 consonants which are correctly observed. If a syllable is used as a unit, 

 the per cent correctly received is termed syllable articulation. 



The discrete sentence intelligibility is the percentage of the total number 

 of spoken sentences which are correctly understood. The discrete word 

 intelligibility is the percentage of the total number of spoken words 

 which are correctly understood. Lists have been prepared for use in 

 articulation testing. These may be used to determine the performance of 

 a system as outlined above. 



*^ Fletcher, H., "Speech and Hearing," D. Van Nostrand Co., New York, 1929. 

 ^ Fletcher and Steinberg, "Jour. Acous. Soc. Amer.., Vol. 1, No. 2, Part 2, p. 1, 

 1930. 



