The purpose of the Noise Regulations 2005 is to make sure that people do not suffer damage to their hearing - so controlling noise risks and noise exposure should be where you concentrate your efforts.
Wherever there is noise at work you should be looking for alternative processes, equipment and/or working methods which would make the work quieter or mean people are exposed for shorter times. You should also be keeping up with what is good practice or the standard for noise control within your industry.
Where there are reasonably practicable things you can do to reduce risks from noise, that are reasonably practicable, they should be done. However, where noise exposures are below the lower exposure action values, risks are low and so you would only be expected to take actions that are relatively inexpensive and simple to carry out.
Where your assessment shows that your employees are likely to be exposed at or above the upper exposure action values, you must put in place a planned programme of noise control.