How to keep from choking my boss???

I am sitting at work, my office is right next to my boss. For the last couple of hours, he has been chewing gum, and popping it, and making that crackly noise with it that some people do. It's driving me insane!! I am on the edge of my seat, my last nerve is just about shot. I can't concentrate on my work knowing that every couple of minutes, I'm going to be subjected to a crackly disturbance. What can I say to him, in a polite way of course, to let him know he is about one pop away from getting strangled 'til he spits out that clump of sticky goo that is the bane of my workday? I thought about saying to him, "Is that gum you're chewing good? It sure SOUNDS like it." But at this point, I think it would come across as sarcastic, and I don't really want to get fired or even to be mean. I'm just interested in stopping the popping!