Can you put spray foam inside a hollow core door to stop sound?

What an interesting idea! I suppose you could, but carefully.

Interesting concept but it won't work Hollow core doors have a honeycomb cardboard interior that provides structure to the doors and prevents them from collapsing. There is no way to fill the honeycomb cavities.

Hi Tra

I was just going to say that it wouldn't work because of the honeycomb cardboard interior - just like William said. I did find an article from a person who actually did it, mainly to test it out. The results were that it worked a little bit but not that much. The door used for testing was going to be replaced with a solid door. The bottom line is that the solid door worked a lot better. Also remember, if you have drywall sound will go through that too. Depending on the room, trying to do the door, might have no affect at all. Click below if you'd like to read the article.

https://www.houzz.com/discussions/2610359/can-i-spray-foam-into-a-hollow-core-door

my brother put it in a hole of an old plaster wall. Then heard “pop”pop” the nails were pulling away from the boards that hold the plaster. Hope the glue that’s holding your door together is strong. Door could warp too.

No, besides it would be extremely messy.

I don't think you would be successful trying to get the spray foam inside all the cavities of the honeycomb inside a hollow core door. You may want to get a sound-proof door instead. Lowe's sells them. They reduce sound by 50%. You could also try putting weather stripping around the door to help with noise control. I hope you find this info helpful. Good luck.