I live in a first floor flat and my downstairs neighbours are quite noisy, and often complain that they can hear noise from me upstairs. I am in the process of completing a renovation of the property and would like to install insulation between the joists under my floorboards to help with the noise and hopefully provide some thermal benefits too. I have been recommended blown bead insulation, and also recommended pouring in sand, but I can't put anything heavy as there is risk it would fall through the ceiling of downstairs. Also a bit bamboozled by all the options online so a bit lost on what to do.
Any advice would be appreciated.