The common case scenario is the camera is placed outdoors where there is no way to determine the correct audio level adjustment. Then when there are high gusts of winds or very loud wildlife activity, the static/crackling noise appears on the live stream audio.
This usually occurs due to an overload on the audio channel specifically to You Tube.
The solution is to reduce the audio gain/output on the Axis cam GUI, to remove the static.
In addition we recommend to set your audio encoding on the Axis GUI to 44.1 kHz and lower the gain a little as well.
If your cam has an Artpec 5 processor then 16kHz is recommended.