After a shoulder arthroscopy I notice a weird pop sound?

Edema. After the scope there will be some swelling. As a result popping, snapping or clicking may be present. As time passes this will resolve.
Recent Surgery? If you just had surgery and are in the early recovery phase this can be entirely normal. We worry more about new squeaking or grinding especially if there has been some recurrent injury. Learn more here: http://www.Theshouldercenter.Com/shoulderpain/2010/shoulder-surgery/shoulder-surgery-complications-an-ounce-of-prevention.
Air. An arthroscopy introduces a good amount of air and fluid into the surrounding tissues and joint. Motion around the joint after surgery cause the air bubbles and fluid to shift around, causing a squishing popping crackling sensation along with very interesting sounds. These will all resolve as the body absorbs the air after surgery. Nothing to worry about!

Related Questions

After post shoulder arthroscopy what does it mean if you hear a pop sound?

Depends on how long. Pops and clicks in the shoulder after arthroscopy can be common and related to the procedure performed. Typically these all resolve by 6 months. Any painful symptoms should always be discussed with your surgeon. Read more...
Pop sound. A pop in the shoulder after surgery usually is indicative of a tendon rubbing over the bone. Read more...
Different things. It could be scar tissue being freed up, hardware abutting other structures, etc. Typically if it doesn't hurt, it's nothing we get too worried about. If your pain was tolerable, but is now worse with the "popping, " that's a red flag. Read more...