I doubt it will be the noise you have .. the roll bar has fixed stops so new bushes if you have play there is a good idea but again i doubt its the cause of a noise .
The most common noise would be the diagonal arms
Best description would be a .. bonk ... bonk bonk over bumps in the road .. if very loud then link rods .. but you can easily feel for play in these whilst you cant in the diag arms .
At the end of the day though .. you shouldn,t have sideways play in the roll bar .