The phrase "frequency vibrations" refers to how often something vibrates or moves back and forth. It describes the rate at which the vibrations occur. Full definition
The engine's high frequency vibration noise also adds a nimble tone, informing the occupants of this vehicle's dynamic driving performance. (www2.mazda.com)
I can also kind of feel the same frequency vibration when I turn the car to the left. (mechanics.stackexchange.com)
The vibrations stay in the pot, because the rope is not stiff enough to carry such high frequency vibrations. (sciencedaily.com)