The aperture mechanism makes a clicking noise when adjusted and is not a malfunction. This sound can be picked up by the microphone of the camera when recording movies.
If the clicking sound is very noticeable, it is recommended that an external microphone with a 3.5 mm diameter mini-plug be used.
Connect an external microphone with a 3.5 mm diameter mini-plug to the camera’s microphone terminal. Maintaining a distance between the microphone and the lens while recording may reduce the clicking sound greatly.
Alternatively, if you do not need to record sound with the movie, you can set the Audio Recording to Off in the menu to disable the camera microphone.
NOTE: If model-specific information is needed for how to turn off the Audio Recording option, refer to the instructions supplied with the product.