As an employer you have a legal duty to reduce the risk of damage to your employees hearing. 

Noise is often defined as unwanted sound. In the context of work, it can be harmful to the human ear and also the physiology of the body.

Loud noise at work can cause hearing damage. Noise (unwanted sound) is measured in decibels. Action levels and limit values have been set for noise exposure.   Noise exposure can be harmful to the human ear and also to the physiology of the body.  Noise at work can interfere with communication.  Hearing damage is often gradual so it may be some time before a person realises that their hearing is damaged.  Employers are required to assess the risk of noise and design appropriate controls to protect employees.