Research Article
Effect of Workplace Noise on Hearing Ability in Tile and Ceramic Industry Workers in Iran: A 2-Year Follow-Up Study
Table 2
Number of subjects with hearing loss in the 1st, 2nd, and 3rd years of evaluation at each frequency considering job category.
| | | Frequency (Hz) | | Study group | 500 | 1000 | 2000 | 3000 | 4000 | 6000 | 8000 | | Right | Left | Right | Left | Right | Left | Right | Left | Right | Left | Right | Left | Right | Left | | | Subjects with hearing loss (, %) |
| 1st year
| Control | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | | 1 | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 4 (2.03) | 0 (0) | 8 (4.06) | 0 (0) | 9 (4.57) | 9 (4.57) | 13 (6.59) | 10 (5.07) | 12 (6.09) | 8 (4.06) | | 2 | 3 (2.67) | 3 (2.67) | 3 (2.67) | 3 (2.67) | 0 (0) | 0 (0) | 4 (3.92) | 4 (3.92) | 12 (11.76) | 12 (11.76) | 2 (1.96) | 4 (3.92) | 0 (0) | 6 (5.88) | | | 3 | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 1 (0.69) | 4 (2.78) | 3 (2.08) | 4 (2.78) | 3 (2.08) | 4 (2.78) | 3 (2.08) | 4 (2.78) | 7 (4.86) | 6 (4.16) |
| | | value | <0.001 | <0.001 | <0.001 | <0.001 | 0.18 | 0.009 | 0.15 | 0.013 | <0.001 | <0.001 | 0.007 | 0.106 | 0.005 | 0.113 |
| 2nd year
| Control | 0 (0) | 0 (0) | 1 (0.98) | 0 (0) | 2 (1.78) | 2 (1.78) | 4 (3.57) | 4 (3.57) | 5 (4.46) | 4 (3.57) | 4 (3.57) | 5 (4.46) | 2 (1.78) | 0 (0) | | 1 | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 6 (3.04) | 2 (1.02) | 9 (4.57) | 4 (2.03) | 15 (7.61) | 15 (7.61) | 14 (7.11) | 17 (8.63) | 12 (6.09) | 13 (6.59) | | 2 | 3 (2.67) | 3 (2.67) | 5 (4.46) | 6 (5.36) | 4 (3.92) | 2 (1.96) | 26 (25.49) | 20 (19.61) | 28 (27.45) | 43 (42.16) | 14 (13.72) | 12 (17.64) | 4 (3.92) | 4 (3.92) | | | 3 | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 1 (0.69) | 7 (4.86) | 4 (2.78) | 7 (4.86) | 5 (3.47) | 17 (11.81) | 8 (5.56) | 7 (4.86) | 8 (5.56) | 7 (4.86) |
| | | value | <0.001 | <0.001 | <0.001 | <0.001 | 0.33 | 0.12 | <0.001 | <0.001 | <0.001 | <0.001 | 0.026 | 0.11 | 0.34 | 0.053 |
| | 3rd year | Control | 0 (0) | 0 (0) | 1 (0.98) | 0 (0) | 2 (1.78) | 2 (1.78) | 4 (3.57) | 4 (3.57) | 5 (4.46) | 4 (3.57) | 4 (3.57) | 5 (4.46) | 2 (1.78) | 1 (0.89) | | 1 | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 6 (3.04) | 4 (2.03) | 12 (6.09) | 8 (4.06) | 17 (8.63) | 26 (13.19) | 18 (9.14) | 21 (10.66) | 20 (10.15) | 18 (9.14) | | 2 | 4 (3.57) | 4 (3.57) | 5 (4.64) | 7 (6.25) | 8 (7.84) | 2 (1.96) | 30 (29.41) | 37 (36.27) | 72 (70.59) | 85 (83.33) | 33 (32.35) | 47 (46.08) | 12 (17.76) | 9 (8.82) | | | 3 | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 1 (0.69) | 12 (8.33) | 11 (7.64) | 20 (13.89) | 32 (22.22) | 37 (26.69) | 31 (21.53) | 37 (25.69) | 14 (9.72) | 17 (11.80) |
| | | value | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | 0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | 0.013 | 0.013 |
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