Soundproofing an apartment -----

[Jon Held]

Hello! I have a soundproofing question.  My new apartment has a sound problem 
- there is an exhaust fan (from a restaurant) near my back door. Much of the 
sound winds up in my apt - mostly mid-range "whining".  It's loud, and 
frustrating.  I want to insulate the back of the apt (on the outside) with 
something.  There is a thin back door, a wall above it which is just 2 layers 
of thin plywood, and a skylight on the ceiling nearby.  

Which material would be best for blocking the sound-
1) Wood
2) Styrofoam, or
3) Standard white ceiling tiles (Don't know what they're made from - 
fiberglass?  I have a few unused ones)

Any advice on this question or other tips on soundproofing greatly 
appreciated.

thanks.

-Jon Held