Spend the extra dough and get cotton sheets. 

They are about as budget friendly you can get when they are on sale.The sheets we use are the Kohl's Big One. 275tc 70/30 cotton/poly blend.

Make sure doors have door sweeps, bushes and trees trimmed away from touching structure, ac lines and pipes going into property are sealed (silicone or steel wool), and general holes into property need to be sealed (hydraulic cement is great for patching stone/cement and steel wool for everything else).Then to tackle the interior issues.

Get some steel wool. 

We recently had a sound transfer problem between two units with an adjacent wall we used mineral wool and a sheet of mass loaded vinyl;  it did the trick.

Usually, you'll have rock wool insulation, newer insulation laid on top.

I suggest you use 100% cotton bond with a watermark, and have someone with nice handwriting address the letter.

For openings use Steel wool and metal with concrete if you can.

Actually, I spent a month there cleaning it out and spent $4,200 on dumpsters tossing drywall and wool ceiling insulation.

@Nathan Zhivalyuk   it looks like it might be rock wool. the joints are not taped as asb joints usually are. can you show a pic of an elbow.