While a separate lawsuit on the use of mid-frequency sonar is pending before the Supreme Court, the Navy and environmental organizations settled a federal district court suit involving low-frequency active (LFA) sonar. The US Navy agreed to limit use of its towed arrays to military training areas in the North Pacific putting about 75% of the world's ocean out of bounds. The agreement was approved by the court today and was welcomed by NRDC and other organizations protecting marine mammals from disruptive and potentially lethal blasts of underwater sound. District court judge LaPorte found previously that the Marine Fisheries Service gave the Navy a permit to use LFA in violation of the Marine Mammals Protection Act and the Endangered Species Act. LFA is used by the Navy to detect lurking submarines that are becoming increasing quiet with technological progress. Low-frequency sound waves can exceed 140 decibels even 300 miles away, a hundred times more intense than any sounds emitted by whales. LFA under the right conditions may be heard across oceans by mammals who also use sound to communicate, navigate and hunt. Independent research shows that decibel levels of 120 are sufficient to affect whale behavior. Seasonal restrictions and mitigating measures will also be observed by the Navy when it uses the sonar. The agreement, in the opinion of activists, proves that a choice between national security and the survival of marine mammals is a false dichotomy.[photo: SURTASS LFA array, U. of R.I.]