The subnucleonic beam was a type of active scan used by Hirogen ships
The Hirogen had the ability to intentionally create a type of subnucleonic beam capable of disrupting an enemy ship's warp engines, communications systems, weapons, and its navigational sensors. Once a target ship was disabled, the Hirogen used their tractor beam technology to draw in their prey.
In 2374, the Class 2 shuttle Cochrane was hit by a subnucleonic beam and hunted down by a Hirogen ship. (VOY: "Hunters")