It's a constant quot;whump, whump, whumpquot; that can be heard from anywhere in the cityIt sounds as if it's coming from Mission Bay, South Beach, or Hunter's Point neighborshoods, but its hard to tellYou can hear it all the way in Twin Peaks.
I was going to say, it probably is the pile drivers working on the Bay Bridge ConstructionMy uncle works supervising the concrete portion of the projectI can tell you that the pile drivers would be working out there every day, unless their machine is broken down.
