Flexible duct behind dryer looks a little sketchy
That looks like standard flexible dryer duct to me. Pull your dryer out and it will probably be connected to the back of the dryer. I would look as there is probably a pipe connection that this flex duct fell off of. I don't think the pipe is a standard flex duct used for HVAC that has an inner and outer flex chamber with insulation in the middle. 
Look close at the bottom left the connection point to the vent may be right there. Connecting the pipe will help the problems you are experianceing when the dryer is running.