Without Risk Assessment (i.e. a consideration of action levels), I can't see how you can take occ.health surveillance forward. HAVS may be another risk.

They only need to do health suveillance if they are exceeding the exposure limits. A noise assessment per se would not give you that information either, only a noise survey would give you accurate information on what levels of noise they are exposed to. But as they work off site (and therefore in variable environments) that is nigh on impossible to achieve.

But may be ineffective when the site changes as accoustics etc affect noise as well as the fact that duration etc may change per job. And by the time you've determined whether limits are exceeeded you'll be onto the next job!

As Ron has stated; without conducting an assessment/survey then you will not know whether health surveillance is necessary.

If noise levels vary by a great deal on a daily basis, then it may be necessary to use dosebadges and get a weekly exposure value; but take note of the peak values as well. Then base your findings/recommendations on that.

Even in relation to people who work in the same environment every day, then their daily exposure may well vary; people move around and may spend slightly longer closer to a source of noise for varying periods each day. So noise surveys have to use an average to some degree, getting tied down with exact daily exposure values is pointless and near on impossible, (as they will undoubtedly vary from day to day). You may well therefore have to base your findings/recommendations on an average or even worst case scenario.