Once you have identified the noise hazards in your work environment, you need to control them to prevent or reduce hearing loss. The hierarchy of controls can help you select the most effective and feasible control measures for your noise hazards. This hierarchy includes elimination, substitution, engineering, administrative, and personal protective equipment (PPE) measures. Whenever possible, you should use the highest level of control and combine different levels of control if necessary. Additionally, you should monitor and evaluate the effectiveness of your control measures and review and improve them as needed. For example, replacing a noisy machine with a quieter one or changing a noisy process with a less noisy one can be an effective elimination measure. Substitution measures include replacing a noisy source or cause with a less noisy one, such as using a different material, tool, or method that produces less noise. Engineering measures involve modifying the source or cause of noise to reduce its noise output, such as installing noise barriers, mufflers, dampers, or isolators. Administrative measures involve changing the way people work or interact with noise, such as limiting the time or frequency of exposure, rotating workers, or scheduling noisy tasks during low occupancy periods. Finally, personal protective equipment (PPE) measures involve providing workers with devices that protect their ears from noise, such as ear plugs, ear muffs, or noise-canceling headphones.