What's that noise?

As I'm sitting in our office, I can hear this noise, and can't help to wonder what the heck is going on outside. It's a known sound... what could it be?

O.M.G. I just remembered this weekend, Montreal is hosting the Grand Prix du Canada! The Circuit Gilles Villeneuve is across the water from here, no wonder I'm hearing noises! At the moment, it's the 2nd free practice session of Formula 1... ok then, mistery solve.

...Oh the joys of living downtown!