CHANGES IX PROGRAM BAND WIDTH 5 



agree with the 5 kc. curve at an abscissa of 8 kc.) A much larger volume of 

 data would be needed to obtain points falling accurately on a smooth curve. 

 To facilitate obtaining the best approximations, the curves were plotted 

 on several kinds of coordinates, including rectangular, semi-logarithmic 

 (shown in the illustrations), probability and logarithmic probability. 



The dotted curves were interpolated between the solid curves and progress 

 in steps of 1 kc. The interpolation was readily accomplished with consider- 



5 8 11 13 15 KC 



Fig. 2 — Music 



5 8 11 13 15KC 



Fig. 3 — Speecli 



Figs. 2 & 3 — Detectability of changes in band width. 



able accuracy. For example, points for the 10 kc. curve are obtained from 

 the values of each of the solid curves corresponding to an abscissa of 10 kc. 

 From these curves, the difference limens for each band width were deter- 

 mined by reading directly the bands corresponding to votes of 25% and 75%. 

 The bands at which these votes occur therefore by definition differ from the 

 reference band by one limen. The following table gives the intervals of one 

 limen as thus derived from the curves. 



