M18x R2 audio issues (crackling/popping sounds)

Hi there. I have an Alienware M18x R2 running Windows 10 Home (1809 build) that I bought used about a month ago. I've been having audio issues with it ever since I got it. Every 1 to 3 seconds, I hear short popping and crackling sounds when audio is playing from any program, regardless of whether it is playing through headphones, the internal speakers or external ones. My sound card also has the ability to record directly from the computer's sound output, and these recordings also pick up the crackling sounds.

I have no idea what to do. I've reinstalled the drivers, changed various audio settings over and over again and installed ASIO4ALL, which some sites say can fix this issue, but all of that was to no avail.

I've uploaded a recording of the crackling sounds to YouTube at this link.

Any help would be much appreciated. Thanks.