6 BELL SYSTEM TECHNICAL JOURNAL 



Differences in Upper Limit of Program Band in KC, Corresponding to One Limen 



Music Speech 



3— 3.6 3— 3.3 



3.3— 4— 4.8 3.4— 4— 4.8 

 4.1— 5— 6 4.1— 5— 6.9 

 5 —6—7.4 4.6— 6— 9.4 



5.8— 7— 9.3 5.1— 7—12.8 



6.4— 8—11 5.5— 8 



6.9— 9—12.2 5.8— 9 

 7.4—10—13.4 6.2—10 

 8 —11—15 6.4—11 

 9.8—13 7 —13 



11 —15 7.6—15 



The difference limens are seen to vary with the frequency of cut-off, in- 

 creasing as the frequency increases. Since each difference Umen corre- 

 sponds to a sensory effect of one Hminal unit, it is obvious that the reciprocal 



UPPER LIMIT OF PROGRAM BAND-KC 



Fig. 4 — Ability to detect changes in program band width. 



of the difference hmen gives the rate of change of hminal units with changes 

 of program band width in terms of hminal units per kilocycle. Therefore, 

 curves of liminal units versus the upper limit of the program band may be 

 constructed from the figures in the table. Such curves are plotted in Fig. 4. 

 The actual mechanics of the process used to plot the curves was as follows, 

 taking the data for "music" for illustration. The lowest frequency occur- 

 ring in the table is 3 kc, and it is seen that raising the band width to 3.6 kc. 

 will bring about a subjective increase of one liminal unit. Therefore, on 

 an arbitrary scale, 3 kc. was plotted at and 3.6 kc. at one liminal unit. 

 Next a smooth curve was drawn through these points and the location of ^.Z 

 kc. (next line of table) was determined by interpolation. Since 4 kc. is one 

 liminal unit above i.Z kc, and 4.8 is one liminal un't above 4 kc, these points 

 were plotted and the curve extended through them. By a similar process 



