When used as an underlayment for hardwood floors or tile, reduces sound reflection and transfer dramatically. Can also be used on walls and ceilings. When installed inside the wall, more than doubles the STC. For instance, a standard hollow sheetrock wall, with 1/2" Gypsum board on metal studs has a STC rating of about 23. (Ordinary conversation through it can be understood). Adding the MLV can increase it to about 53! (Loud shouting is not heard). Just staple or glue the material to the wall, then cover with sheetrock- tape off and paint. Want more sound reduction? Use a double layer of MLV!