Wiktionary
subfrequency
n. A secondary or subsidiary frequency.
Usage examples of "subfrequency".
New Republic comm units, by reducing voice data to the smallest set that would convey data and be recognizable, were able to broadcast transmissions across a wider set of subfrequencies, making it more difficult for enemies to jam them.
You know as well as I do that Betazoid telepathy is subfrequency and seems supernatural, but that it’s perfectly explainable scientifically.