Has anyone ever heard it? Is it load? Could you hear it with a sled running, In motion?
the last time I heard the whump, we were riding on a flat meadow in the mountains, I was parked and a sled went by me and the snow made the noise, you don't have to be in the big hills to have this happen.
Its air pocket in the layers of the snow, generally in areas with alot of windblown snow.
I've experienced it many times, but the worst was probably when sbr and i were up in renshaw on one of our first trips, before any avy training was even available, and we were both stuck up high on a heavily loaded slope and 3 feet fresh powder, and we were just unpacking to start shovelling and felt and heard the loud whumph.... Eerie, at the time, and back then we never thought much about it, and there wasn't any one else around us at the time......... Could have been real bad, real quick