LOL Issues

I'm working on the second half of my Six Flags/Chol Ha'moed post but now I've got something else on my mind.

My laugh is not office appropriate.

Although the company I work is a bit stodgy my co-workers are a professional but fun (and funny) group. Part of this is because our boss is so moody and quirky that humor is the fastest and easiest was for us to keep each other motivated - but mostly it's just a smart and clever bunch of people who get along really well and have loads of material from right around the office.
I have a very easy laugh and when something strikes me funny I am likely to bust out laughing. As I find my self laughing loudly and often to the whispered jokes and wacky antics of our boss (everyone's favorite is his loud cry of "I'm SOOOO busy!" which is what he says right before he closes his door to make long personal calls which we can all hear through his door) I find myself realizing that I've never cultivated an office appropriate laugh.
Believe me, I've heard worse, my laugh isn't some kind of whinny or snort, just friendly and a bit louder than I'd like at times...

Any advice on how I can it down when jokes catch me off guard?