10 BELL SYSTEM TECHNICAL JOURNAL 



speech lies between the figures given in the table for male and female speech, 

 which is a good check. 



The present tests did not include measurements on the lower end of the 

 frequency band. However, some clue to the results that would be expected 

 may be obtained from Mr. Snow's paper. Table II, derived from Mr. 

 Snow's data in a manner similar to that just described, gives the lower limit 

 of the frequency band corresponding to a degradation of one liminal unit 

 compared with transmitting a much lower frequency. 



The frequency corresponding to one liminal unit for speech may be taken 

 as the mean of the figures for male and female speech, or about 150 cycles. 

 In the case of music, it may be expected that at the lower as well as the 

 upper end of the frequency range one liminal unit for an orchestra should 

 fall about one third the way down the list of individual instruments, and two 

 liminal units about two thirds the way down the list. This would make one 

 liminal unit for music correspond to about 80 cycles and two liminal units to 

 about 150 cycles. This speculation leads to the interesting hypothesis 

 that the relations are probably the same at the lower as at the upper end of 

 the frequency scale, that is, changes in band widths are twice as readily de- 

 tected for music as for speech, and that the frequency limit corresponding to 

 one liminal unit for speech corresponds to two liminal units for music. 



