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BELL SYSTEM TECHNICAL JOURNAL 



of tests used in obtaining the mean values is given in the right-hand 

 column. For each age group, they were selected in a random manner 

 from the New York and San Francisco tests, about two-thirds from 

 New York and one-third from San Francisco.^ 



Certain trends in average hearing are evident in Table 2. On the 

 average, both men and women show increasing hearing impairment 

 with increasing age. For high-frequency tones, and especially at 3520 

 cycles, the effect is more pronounced in men than in women, but for 



440 



880 1760 3520 



FREQUENCY IN CYCLES PER SECOND 



7040 



Fig. 3 — Mean hearing loss in db for men and women in the youngest, middle, and 



oldest age groups. 



low tones the opposite is true, although to a smaller degree. For the 

 1760-cycle tone there appears to be little difference between the 

 hearing of men and women. These trends are shown in graphical 

 form in Fig. 3, for the youngest, middle and oldest age groups. 



At the lower frequencies, the hearing of the youngest group in 

 Table 2 is slightly poorer than that of the next older group. It is 



* Several sampling procedures were used, all based on selection of tests by some 

 arbitrary rule, such as taking four tests in order then skipping twelve. In general, 

 the same rule was used throughout a whole day's tests. The days selected were well 

 scattered throughout the season, and week days and week-end days were used in the 

 proper proportion. A larger sampling proportion was used for the older age groups, 

 to make the groups in the sample more nearly equal in size. 



