straight forward health and safty advice 
Your hearing is valuable to you, however if you are subject to loud noises, your hearing may be damaged This damage may be short term and your hearing can recover, but if the noise is very loud or occurs over a considerable period, your may not fully recover your hearing. If you are in a noisy area where two people standing 2 metres (6ft 6ins) apart would have difficulty in hearing each other speaking in a normal voice, or have to shout to be heard; or if you are using noisy powered tools or machinery for more than half an hour each day, then your hearing could be damaged. You should use suitable ear protection in these circumstances. Some work areas may be designated as “hearing protection zones” and be marked with signs. You must use hearing protection when working in, or entering the zone – failure to do so, will damage your hearing. Items of plant and equipment that may damage your hearing are generally marked to show that hearing protection should be worn when near them, or while using them. Although not marked, some hand held power tools may be very loud if they are used near your ear, drilling near your head, for example. Follow the 2 metre rule given above, if people have to shout to make you hear, use ear protection. People often experience temporary deafness after leaving a noisy place. Although hearing recovers within a few hours, this should not be ignored. It is a sign that if you continue to be exposed to the noise, your hearing could be permanently damaged. Permanent hearing damage can also be caused immediately by sudden, extremely loud, explosive noises, e.g. from guns or cartridge-operated machines; but hearing loss is usually gradual because of prolonged exposure to noise. Remember, simple things like switching off machines when they are not in use, and checking all bolts, fixings, removable covers, etc  are kept tight to prevent vibration and rattling noises, all help to keep noise levels down.
Work precautions