An interferometric pulse was an energy emission produced by individual vessels of a species native to the Delta Quadrant, which acted as a lattice connecting all of the ships to each other. The pulses had the ability to cancel out a vessel's shields by modulating in opposition to the shields' frequencies, and to reflect the energy of particle weapons back to the attacking ship.
In 2372, the USS Voyager encountered this species while attempting to covertly cross their territory. Voyager was nearly defeated, but the crew was able to modulate their shields to an inverse harmonic of the interferometric pulse, allowing them to fire ship's phasers at one of the attacking vessels without having the energy reflected back at them. Upon firing on one of the ships, the pulse that linked them together caused a chain reaction in the swarm, which subsequently disbanded and moved away from Voyager. (VOY: "The Swarm")