Citing national security interests, the U.S. Supreme Court ruled on November 12 that the Navy can once again conduct sonar training exercises, even if the tests harm marine life. The 5–4 decision overturns restrictions that require the Navy to stop using sonar when marine mammals are spotted within 2,200 yards of its vessels. The Navy uses sonar technology to send underwater sound waves at frequencies between 1 kHz and 10 kHz. Gauging the time it takes the acoustic waves to echo off an object — enemy submarines in a combat situation — provides a way to determine the distance to the ...