Do it right

I’m not a builder so will be getting someone to fix my problem. I had triple glazed windows fitted pre lockdown. However, I felt the noise level was worse than previously. The installer said foam should have been fitted in gaps but when I removed the hardboard reveal, I saw there was nothing there. A local window fitter came and put some foam in but noise level is still bad. what’s my best solution ? what’s the best type of reveal? Board or have it plastered?