Astar very loud startup static noise  

Curious if anyone else here may have experienced this before.  When we hit the starter on a B3e, there is a very loud static noise...it lasts for about 5-10 seconds before going away.  To make things more interesting, the static noise does not occur if starting from a start stick or other external power source. 

The static can't be traced to a single audio source, as it occurs regardless of which audio source is selected.  The only way to silence the static is to unplug my helmet/headset. 

We are stumped...anyone else experience this before?  Thanks in advance.