Borei class includes a compact and integrated hydrodynamically efficient hull for reduced broadband noise and the first ever use of pump-jet propulsion on a Russian nuclear submarine. Russian news service TASS claimed the noise level is to be five times lower when compared to the third-generation nuclear-powered Akula-class submarines and two times lower than that of the U.S. Virginia-class submarines. The acoustic signature of Borei is significantly stealthier than that of the previous generations of Russian SSBNs, but it has been reported that their hydraulic pumps become noisier after a relatively short period of operation, reducing the stealth capabilities of the submarine.