That is the sound you may hear when you are cracking your knuckles or other joints. I have always wondered why some people need to crack their joints all the time while others never need to. Also, why does it make a noise when you do crack your joints? One reason it makes a noise is because gas escapes. In order to crack it again you have to wait for the joint to make another gas bubble. You may also hear a cracking sound when joints, tendons, and ligaments slide out of place. The last reason is when you have arthritic joints. There is a lack of cartilage in the joints so it makes a noise.