Good day @jan_stolzenberg , Your G4 makes very strange sounds, I have never encountered anything like this. I think you need to contact aqara support or wait for a comment here from the product manager. Here is the email of aqara technical support. support@aqara.com
Mine has started doing this exact same thing a couple of weeks ago. I originally installed it about 17 months ago and it worked flawlessly up until it started making this noise.
I have just checked again and after some app update or Alexa skill update now the Aqara cameras are not emitting sound when viewed from Alexa app on my Android phone.
But the sound is still emitted when I view the cameras on my LG TV via Alexa Cube.
I think the issue may be because I can’t enable or disable the microphone and this is probably some mic feedback on a loop.