plug up the opening of a 2" cable conduit for soundproofing

Give it a "shot" of spray foam in each end

how about clean rags or towels? plumber's putty would do the job but it's messy. it would slow down water and insects.

Good solution, but it does tend to cling when you want to remove it, so insert a thin plastic bag first, and spray the foam into that.

Go to your local electrical supply place and get some of the 3M fireblocking material that is designed for the purpose. Putting some steel wool in there before you pump the stuff in is also a good idea; it will keep mice and gophers out.

--scott

I've used a rag with a stout cord stuffed in first, followed by children's play clay, oil based. The rag will drag out the clay, when you need to. The clay never dries out.

Steve King

You need Ducseal, known more commonly in the trade as monkey s*it.

Monkey s*it is very much like modelling clay

Hmm 2" conduit ? How about a condom?

Well - is there a possibility you will have more cables to pull in the not so distant future? In any event it is a good idea to leave a rope or dedicated wire in your cable conduit for an easy install the next time you have to do a cable pull - and this has turned out to be a regular thing in some places I have worked, especially in the conduit between a machine room and the control room. Also you can just cover the conduit hole with a large heavy duty Sandbag or two, such as are commonly used in Stage and Video production applications. This is I think less messy and more efficient in reducing sound transmissions than putty or "Stuff" foam, assuming you can cover the hole and cables fully. You can also build a box to cover the sandbags if you find them unsightly or in the way.

Cheers,

Will Miho NY TV/Audio Post/Music/Live Sound Guy "The large print giveth and the small print taketh away..." Tom Waits