. The Bell System technical journal . ge groups is shown in Table 2. The number TABLE 2Mean Hearing Loss in db Frequency Age Group Number of Tests 440 880 1760 3520 7040 Men 10-19 .3 4132 20-29 .0 3287 30-39 3197 40-49 4528 50-59 1935 Women 10-19 .5 .2 3417 20-29 .0 .2 .1 4208 30-39 3978 40-49 4369 50-59 2538 538 BELL SYSTEM TECHNICAL JOURNAL of tests used in obtaining the mean values is given in the right-ha
. The Bell System technical journal . ge groups is shown in Table 2. The number TABLE 2Mean Hearing Loss in db Frequency Age Group Number of Tests 440 880 1760 3520 7040 Men 10-19 .3 4132 20-29 .0 3287 30-39 3197 40-49 4528 50-59 1935 Women 10-19 .5 .2 3417 20-29 .0 .2 .1 4208 30-39 3978 40-49 4369 50-59 2538 538 BELL SYSTEM TECHNICAL JOURNAL of tests used in obtaining the mean values is given in the right-handcolumn. For each age group, they were selected in a random mannerfrom the New York and San Francisco tests, about two-thirds fromNew York and one-third from San Francisco.^ Certain trends in average hearing are evident in Table 2. On theaverage, both men and women show increasing hearing impairmentwith increasing age. For high-frequency tones, and especially at 3520cycles, 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 the1760-cycle tone there appears to be little difference between thehearing of men and women. These trends are shown in graphicalform in Fig. 3, for the youngest, middle and oldest age groups. At the lower frequencies, the hearing of the youngest group inTable 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 somearbitrary rule, such as taking four tests in order then skipping twelve. In general,the same rule was used throughout a whole days tests. The days selected were wellscattered throughout the season, and week days and week-end days were used in theproper proportion. A larger sampling proportion was used for the older age groups,to make the
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