Popping/plucking noise in cockatiels

[Hannah22]

I just rescued a beautiful cockatiel. He has not yet seen a vet for a well was check since I acquired him, but previous owners said he had one done about a year ago. I've noticed a strange popping noise sometimes, can't tell if it's physical, respiratory or what. It's been years since I owned a cockatiel, is this a normal noise for this type of bird or should it be checked out?

[Pajarita]

None of the tiels I've had have made a popping sound.