I just moved into a home in Wheaton, IL. The house is great except for one thing: you can easily hear through the walls. For example, the master bathroom was placed along the main hallway, and you can hear... everything... not what you want when entertaining guests!

I've read about folks reducing noise by making a small hole in the wall and blowing foam in between the 2x4's. As the foam is added, it expands and significantly reduces the flow of noise.

Any comments on how to do this? Would the above work? I image any insulation would help, and a 1/4" hole + spray-in foam seems the simplest way to go.

Thank you for your guidance.