Intro to health surveillance
The risks from noise are pretty much entirely focused around the health of individuals so naturally the health side of things features heavily in the regulations and what they are trying to achieve. Regulation 9 of the Noise Regs says that you needs to have a programme of health surveillance for anyone who remains at risk of noise while at work, meaning anyone who is still exposed to over 85dB(A) or 137dB(C), ignoring the reductions offered by the hearing protection. (The last bit in italics is important - it means you have to provide hearing tests for anyone working on a job which is exceeding the 85dB(A) limit, even if they do wear hearing protection all the time).
The two issues involved in the whole noise exposure malarkey are hearing losses (referred to as noise induced hearing loss, NIHL) and tinnitus. Back in the good old days of the three day working week and men standing around fires in old oil drums on strike outside a factory, NIHL was called Industrial Deafness. Tinnitus meanwhile is the sensation of noise in your ears which isn't really there. Both are covered in more detail in the page on the effects of noise on hearing.
Health surveillance means audiometry
In practice, when the noise regulations say that an employer needs to have a programme of health surveillance in place for at-risk employees, (sometimes called a health screening programme), what they are talking about is audiometry, or hearing tests as normal people call them. That's the 'hear noise press button' thing that people probably had at school, minus the free lollipop. You can do these yourself or get someone in to do it. Unless you have the full set up in-house, it's easier to just get someone in and to help you, here is a page on how to choose an audiometry provider.
Audiometry is a continual process
Audiometry is an ongoing programme rather than a one-shot jobby so is something which will need to be set up and maintained as long as you have high noise areas in your work. The links at the top of this section will give you a shed-load of information on audiometry, how to set it up, how often to do it, who should do the tests for you, compulsory attendance, the murky world of medical confidentiality which it takes you into, and so on. Have fun. If you have a question which is not covered by any of those pages, please just let me know and I'll be more than happy to try and help and add it to the site.