While testing bearings at a major mid east cereal manufacturer high ultrasound readings were recorded on one of 7 cookers. After lubricating the bearing with the prescribed amount of grease the ultrasound readings did not change. The machine was flagged for service and the bearings changed out.
Later it was discovered that the thickener had separated from the grease and clogged the cage preventing new grease from reaching the rolling elements of the bearing.
Don't just grease bearings with ultrasound, diagnose unusual problems too.