re: Ideas for better soundproofing bedrooms?

Look into RetroFoam of Louisiana, they do an injection foam specifically for older houses. Can go through the exterior walls or in your case, drill holes in the drywall and fill the cavity that way. Before I found out about them I had all of my baseboards up in my 100 year old house and went to Home Depot and rented an insulation pumping machine and bought bags on the recycled material insulation. My 1 year old son’s bedroom is next to ours and we can’t hear him crying at night between the walls. Just on the monitor.