STANDARD VOLUME INDICATOR AND REFERENCE LEVEL 127 



A small but important feature of the new scale is the use of an arc 

 to connect the lower extremities of the vertical black division marks. 

 This arc affords a natural path along which the eye travels as it watches 

 the needle flash up and down the scale. The omission of this arc 

 would result in a number of vertical division marks, hanging in space, 

 as obstacles to the free back-and-forth motion of the eye. 



It is evident, upon comparison of Figs. 12, 13, 14 and 15 with Figs. 

 16 and 17, that the dynamic volume range visible on the scale is at 

 least twice as great as on former instruments. This range, as already 

 explained, is a good median value for general use. 



Mention was made of the opinions of a group of skilled observers. 

 This group consisted of more than 80 broadcast technicians who, in 

 the performance of their duties, watch volume-indicator instruments 

 almost continuously throughout the working day. The opinions of 

 this group were obtained by submitting working models for their 

 individual considerations. It is believed that some of the results of 

 these observations are of interest. 



1. 83 per cent preferred the cream in place of a white scale card. 



2. 90 per cent preferred the "0-100" scale to the "0-60" scale. 



3. 92 per cent preferred the longer scale length (3.5" vs. 2.36"). 



4. 97 per cent preferred the numerals placed above the arc. 



5. 50 per cent preferred the spade pointer to the lance type. 



6. 93 per cent agreed on the adequacy of 3 db leeway above the 

 reference point. 



New Reference Level and Terminology 



Having agreed on the characteristics of the new standard volume 

 indicator, the interests of complete standardization call for agreement, 

 as well, upon a uniform method of use and a uniform terminology. 

 Agreement upon a uniform method of use must include establishing 

 the reference volume or zero volume level to which the readings are 

 to be referred and agreeing upon the technique of reading the volume 

 indicator. 



It is important to appreciate that "reference volume" is a useful 

 practical concept, but one which is quite arbitrary and not definable 

 in fundamental terms. For example, it cannot be expressed in any 

 simple way in terms of the ordinary electrical units of power, potential, 

 or current, but is describable only in terms of the electrical and dynamic 

 characteristics of an instrument, its sensitivity as measured by its 

 single frequency calibration, and the technique of reading it. In 

 other words, a correct definition of reference volume is that level of 



