Question Intermittent Static Audio over HDMI

Aug 31, 2020
Hi all,

First, my equipment:
  • MOBO: ASRock B450M HDV r4.0, all default settings, no OC tweaks
  • CPU: AMD Ryzen 5 3600
  • GPU: RX 570
  • Case: Thermaltake Versa H18
  • OS: ubuntu 20.04 LTS. Audio server is regular pulseaudio stuff
Every so often, after my PC has been on for a day or so (with or without standby), hissing, crackling static gets added to the audio stream from the HDMI out. The volume of the static scales in proportion to the loudness of whatever's being played, and when no audio is being played, even in the silences within an audio track, there is no static. This doesn't happen if the audio equipment is plugged into the 3.5mm audio out jacks on the motherboard or the case. Sometimes the problem goes away on its own, restarting the computer seems to fix it. Things I've tried to rule out problems
  1. This happens with multiple HDMI cables, both with and without ferrite noise filters
  2. This does not happen to another source (PS4) plugged into the same receiver while the PC is receiving the problem
  3. This does happen when plugged into another receiver
  4. This still happens when all equipment is plugged into the same power strip
  5. This happens whether the audio is played through headphones or speakers, both of which work on other sources
  6. This happens to all audio played from the computer, regardless of software source
  7. Restarting the pulseaudio server does not fix the issue. Login/logout and sleep/wake both do not fix the issue. Only reliable fix seems to require a complete shutdown, indicating the problem is some kind of physical electrical noise
The sketchiest thing I've done is, after having intermittent random shutdowns and no-POSTs related to MOBO shorts and noticing that one of the case standoffs had what looked like exposed protruding steel, I added some electrical tape over the standoffs to try and create proper insulation. This definitively fixed the shorts, but maybe it's related to my audio problems?