Good to know but what about windows what type? 3 sheets of glass or laminated glass that would cost a fortune.You don't want anechoic. You want sound isolation. a common technique is to minimize the windows and doors and using heavy doors and windows when you need to have them. Spray foam within all exterior walls. RSIC clips or similar with hat channel off of all studs and joists and hang double layers of 5/8" drywall with green glue in between. All floors have green glue between two layers of subfloor and also a mass-loaded vinyl layer for vibration dampening.