I totally agree with BNJVisuals. This is an obvious issue with Safari. My version 14.1 (14611.1.21.161.7) on Mojave 10.14.6. By comparison Chrome version 90.0.4430.212 (Official Build) (x86_64) (on the same computer and Mojave version) do not have any problems with popping or cracking sound.
Apple engineers, please get off your ***** and finally fix these code bugs!
Little update:
Killing coreaudiod works for me as well. The question is: for how long..?