In a triumph of the military over the environment, the U.S. Navy yesterday won approval to deploy two ships that use low-frequency sonar to detect distant submarines, despite ongoing fears that the system could injure whales and other marine mammals. The National Oceanic and Atmospheric Administration granted the Navy an exemption from federal rules protecting marine mammals, saying the likely effects of the sonar would be “negligible” as long as protective measures were followed. The new sonar system creates a noise similar to a Boeing 747 at takeoff, a sound everyone agrees would injure nearby marine mammals. The NOAA ruling, however, requires the Navy to use visual sighting and passive sonar to make sure that no mammals are within 1.1 nautical miles when the sonar is used. But environmentalists question whether that will sufficiently protect whales, dolphins, and other sea creatures; the Natural Resources Defense Council said it might sue to overturn the ruling.