Thank you for posting and welcome to the Community!
Sorry to hear about this crackling noise you're experiencing. I just want to clarify which cable connection you're currently using. If you have a spare HDMI or Optical cable try swapping the cable out to see if the issue goes away.
Let us know the results.
Joel - Community Support
Thanks for testing that. If it's happening with Alexa, it sounds like there is an issue with the Soundbar, and not how you've set up the system. I would recommend you contact your local support center via phone to arrange for a replacement. To do this, select THIS link, choose your country, and scroll to the bottom to "Contact Us".
Please let us know if you have any other questions.
Brandon - Community Support