Metallurgy / Environmental Monitoring / Noise Induced Hearing Loss / Human Resource / High Frequency / Humans / Female / Male / Hearing Loss / Risk factors / Clinical Sciences / Middle Aged / Occupational / Adult / Occupational Exposure / Public health systems and services research / Multivariate Regression / Risk Factors / Occupational Diseases / Cross sectional Study / Occupational and environmental medicine / Humans / Female / Male / Hearing Loss / Risk factors / Clinical Sciences / Middle Aged / Occupational / Adult / Occupational Exposure / Public health systems and services research / Multivariate Regression / Risk Factors / Occupational Diseases / Cross sectional Study / Occupational and environmental medicine