My Iphone SE2020 has a clicking Sound during calls

The click sound is only audible on the phone‘s speakers when I hold it close to my ear. Not on my loudspeaker function speakers. The click sound is repetitive and constant in a rythm with about 1-2 seconds in between. It is very loud on the other side but also annoying and audible for me.

Description‘s of the camera‘s aperture being the reason sounds somehow inagineable. It is only a theory though. This phone is a refurbished one but it didn’t have the Problem from the beginning…

Running the latest

iOS 16.1.2 (20B110)

Hope anyone can help or has the same Problem?

Oscar