“…37% abnormal PTA, 65% abnormal HFA.
Significant association with years worked and age.presbycusis, small sample. | Ostri et a1. 1989 [102] | Case series | 95 orchestral musicians 80 males, 15 females age 22–64 | 0.125, 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8 kHz (PTA) | >20 dB average hearing loss in either ear | 44% of musicians had hearing impairment attributed to occupational noise exposure. Significant poorer hearing on the left ear found at higher frequencies among violinist. | instrument played, side of orchestral band, previous noise exposure |
Cox et a1 1995 [63] | Case series | 235 soldiers with past weapon noise exposure age 16–55 | 0.5,1, 2, 3,4, 6 kHz (average single frequency threshold) | Interaural difference = asymmetry >10 dB | 67% asymmetry at 4 kHz. Average hearing loss and interaural asymmetry increased with frequency. | handedness, emotional immaturity, motivation for army service, use of ear defenders |
Pirila et al 1992 [109] | Cross-sectional study | 3487 random people 1640 males, 1847 females 3 age groups (5–10,15–50, >50) | 0.125, 0.25,0.5,1, 2, 3, 4, 6, 8 kHz (average single frequency threshold) | Interaural difference = asymmetry >0 dB | The inferiority of hearing in the left ear at 4 kHz seems to be assiciated with noise damage. The average interaural difference at 4 kHz was more marked in age 15–50. | shooting history occupational noise exposure |
Pirila et al 1991 [98] | Cohort study | 28 non-shooting normal HL 10 males, 18 females age 17–29 exposure to broad band noise 88–91 dB for maximum 8 h | 4 kHz (average single frequency threshold) | determine TTS after noise exposure | TTS was greater in the left ear than the right. Negative correlation between pre-exposure threshold level. | rely on history, samll sample size. |
Chung et al 1983 [95] Audiology | Case series | 1461WCB claims for NIHL no head injury, no ear surgery age 36–82 | 2 kHz (average single frequency threshold) | >20 dB | 4.7% has asymmetry, suggesting damage toward apex. 82.6% has worse hearing thresholds in the left ear. 2 kHz is lateral difference in susceptibility to noise damage. | limited frequency considered |
Nageris et al 2007 [103] | Case series | 4277 army personnel files age 16–55 | 3–6 kHz (PTA) | mild loss = 25–40 dB HL moderate loss = 41–60 dB HL severe loss = 61–90 dB HL asymmetry = different grade | 50% symmetrical. 34.2% left asymmetrical NIHL. |
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