They refer to "natural frequency of the calcium carbonate" - no such thing. There are plenty of frequencies related to vibration of bonds in CO32- and to modes of vibration of the whole anion, there are definitely frequencies of vibration related to the solid CaCO3, but there is no single frequency at which calcium carbonate can resonate, this is just made up, some buzz words thrown in and combined together.
I remember reading a published, peer reviewed paper stating that magnetic field (just a static one, no frequencies involved) can promote early precipitation of the scale in the water, so that it becomes sandy and gets easily flushed out from the pipes (instead of building a solid on the surfaces). But if memory serves me well that was just a single publication, not sure if anyone reproduced the effect.