i haven't popped any zoom air bubbles on my tennis shoes (air max a few times) but it's happened a lot with my basketball shoes. if the zoom air bubble popped, it should be very noticeable when you wear it, especially when comparing one shoe to the other. it'll feel flat and your foot should be able to feel where the inflated zoom air bubble used to be. zoom air is a pressurized bag, so even a small hole will completely deflate it, whereas max air can still maintain some shape even with a huge hole. you can also check by pressing up on the outsole when wearing it or pushing down from the insole. with that said, i've never had a crackling sound. maybe it's rubbing up against something in the shoe?
regardless, if it's really popped, you can send them back as long as it's within 2 years of manufacture date (the date on the bottom left of the tag) and they'll send you a voucher since it's considered defective