502 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1924 



weak have values of 84 or better. On the whole the sounds "th," 

 " f ," " s," and " V " are hardest to hear correctly, and they account 

 for more than half of all the errors of interpretation. In general, 

 it is observed that the volume at which errors begin to be large 

 is different for different sounds and is usually higher for the con- 

 sonants than for the vowels. Within the precision of the data. 



/^ihpeoxLouorYESS i^poeox Louo/yESs /^A>pffox lauD/y£5S , 



Fio. 7. — Articulation — Loudnesa curves for some typical speech sounds 



the intersections on the axis of abscissas all correspond with the 

 threshold of hearing. 



The effect of frequency distortion has been investigated by insert- 

 ing several systems of electric-wave filters in the high-quality ex- 

 perimental circuit. Articulation results with low-pass and high- 

 pass filters are shown in Figure 8. The ordinates show the per 

 cent of syllables called which were correctly recorded at the re- 



