LOUDNESS 



417 



analyzed, this tone was found to have the voltage level spectrum 

 shown in Table XIV. When the r.m.s. voltage across the receivers 

 used was unity, that is, zero voltage level, then the separate com- 

 ponents had the voltage levels given in this table. Adding to the 

 voltage levels the calibration constant for the receivers used in making 

 the loudness tests gives the values of /3 for zero voltage level across the 

 receivers. The values of /3 for any other voltage level are obtained by 

 addition of the level desired. 



TABLE XIV 

 Voltage Level Spectrum of No. 3A Audiometer Tone 



Tests were made on the audiometer tone with the same receivers '' 

 that were used with the other complex tones, but in addition, data were 

 available on tests made about six years ago using a different type of 

 receiver. This latter type of receiver was recalibrated (Fig. 13) and 

 computations made for both the old and new tests. In the older set 

 of data, levels above threshold were given instead of voltage levels, 

 so in utilizing it here, it was necessary to assume that the threshold 

 levels of the new and old tests were the same. 



Computations were made at the levels tested experimentally and a 

 comparison of observed and calculated results is shown in Table XV. 



The agreement of observed and calculated results is poor for some 

 of the tests, but the close agreement in the recent data at low levels 

 and in the previous data at high levels indicates that the observed 

 results are not as accurate as could be desired. Because of the labor 

 involved these tests have not been repeated. 



At the time the tests were made several years ago on the No. 3A 

 Audiometer tone, the reduction in loudness level which takes place 

 when certain components are eliminated was also determined. As this 



'1 See Calibration shown in Fig. 1. 



