Like I said, regulators do not make any sound if water is not flowing. If the regulator is in close proximity to your water meter you may want to check it. Some meters have a built in spring check valve that can make clicking noises, when water is flowing.
With all the fixtures in the house off look and see if the leak detector, on the meter, is moving. This will tell you if there is water is flowing or not. Even with all fixtures off there may be a small leak giving you flowing water.
Often times the meter can make noise and the noise can travel and seem to be coming from somewhere else.