Your players may hate you for this...
... that is, if they find out you've been using it!
It's an hour long sound, a 19 Hertz sine wave. Most people cannot even hear it at all, a few can especially if it's played very lound, but it is just about too deep to be perceived. Consciously, that is. Sound at this frequency has been shown experimentally to cause feelings of uneasiness or anxiety, even when people don't know its there. Some people have associated it with haunted places - you can find it as a resonant frequency in fans or heating ducts sometimes... oh, and 18 Hz is the resonant frequency of your eyeball, which COULD explain some of those ghostly things you see out the corner of your eye!
If it's played loud enough, people may feel it rather than hear it. But they have been reported to suffer headaches or earache, so be careful. (If you know urban legends relating to low-frequency sound, this is too high pitched to be a 'brown note' - one that can cause people to, er, lose control of themselves, that is supposedly about 5-9 Hz.)
Do you want to make your players feel a bit uncomfortable, a bit ill-at-ease? Then you might want to experiment with playing this during a game. Better be prepared to run, they might lynch you if they ever find out.
Look, it's a freebie. It may be fun. It may help your next spooky game get the right atmosphere. It may even amuse you to watch your players...