OSX loud siren that starts every 1-5 minutes?
Does anyone else have access to your iCloud account?  If they do, they can play a loud noise using Find My Mac.  If you've recently received an email notifying you that someone has signed into your iCloud account using a web browser, that would be an excellent sign that the Find My Mac siren is what you're hearing.

Another possibility: Did you install Prey Project on your Mac? It's a piece of software similar to Find My Mac, and it can produce a very loud siren noise.  Check your Prey account settings; if someone else has access to the account, they can play a siren noise.