cracking sunnies?

Sabine

O.G.
Apr 12, 2006
2,275
4
I have made my first chanel purchase, a very nice pair of sunnies. I don't the name but they are brown with the logo in a circle on the side. I noticed the sunnie make a cracking sound if you put it on or move the sides, the other pair in the store did it twom is this normal?
 
None of my Chanel sunglasses do this but two pairs of my Oliver Peoples do. I don't know what causes it but they are still intact, no breakage.