STANDARD VOLUME INDICATOR AND REFERENCE LEVEL 115 



Fig. 9. The 50 per cent point on the curve is interpreted as indicating 

 the level of the test program at which it appears to the average observer 

 to have the same loudness as the reference program. The test pro- 

 gram is then set at this "equal loudness" volume level and the levels 

 of both test and reference programs are read with each of the types of 



o 



u. 50 

 O 



-10 -a -6 -4 -2 2 4 6 8 



VOLUME LEVEL RELATIVE TO THAT OF MALE SPEECH 



Fig. 9 — Per cent of observers choosing symphony music at indicated volume 

 levels to be louder than the male speech reference. 



volume indicators of interest. In this way, the figures given in Table 

 IV were determined. 



It is evident from the figures in the table that there is no significant 

 advantage for either type of volume indicator where loudness is the 

 criterion. 



Table IV shows that when the new volume indicator is used the 

 musical programs must be 2 to 3 db higher than speech to sound equally 

 loud. It is of interest to note that according to Table I this same 



