There are windows on the left side of the room my HT is in and once every few months a military helicopter will fly near our house. My son and I were watching the Seth episode of Stargate SG-1 season 3 on DVD. In the episode, there is a military helicopter that flys by off screen from left to right. Neither one of us could tell whether the helicopter was real or not until the sound moved to the right side of the room. We just looked at each other and said Wow!