This probably isn't the best place to ask me this, since that guide does have its own comments section, but it looks like it's due to this issue. https://itch.io/t/5229926/decker-makes-constant-clicking-sound-on-one-of-my-comp...
Short version: it is a bug in certain versions of SDL2. Fixing it may be up to your distro upgrading to a version that fixes the bug.