BD have battery-powered robots much quieter than the gas-powered Big Dog: Handle (https://www.bostondynamics.com/handle), Spot (https://www.bostondynamics.com/spot), Atlas (https://www.bostondynamics.com/atlas)
Spot was mentioned in the article you linked to as being quieter but able to carry less weight and less autonomous than Big Dog.
The Marines are resuming limited testing with a version of Spot upgraded for greater autonomy in 2018: http://www.military.com/daily-news/2017/04/05/spots-back-mar...