If it happens in my AmeriQue I’ve never heard it, but then I’m a set it and forget it kind of guy so I not usually around after I put the meat inside
The closest I’ve come was at the beginning of cold smoking cheese and I opened the door and, as Mr T described, when the air rushed in the wood chunks burst into flames but with a loud whooshing sound. When I closed the door the flames and smoke died back and everything was normal.
I believe the “boom” is the wood chunks igniting and rapidly dying back