A British thermal unit (Btu) is a standard unit of energy that is used in the United States and sometimes in the U.K.
There is another defect in tires that can cause a vibration called loaded road force variance. The tires and pass a visual inspection, a radial and lateral runout test, be perfectly balanced, but still cause a vibration. This is due to the internal defects in the tire.
The majority of vibration problems are caused by the wheels or tires being out of tolerance in some way, usually because of an impact. When I go to diagnose a vibration, I always check the wheels first, then the tires, followed by alignment and suspension.