The Navy was expected to release its full findings Friday.
The Navy estimates its use of explosives and sonar may unintentionally cause more than 1,600 instances of hearing loss or other injury to marine mammals each year, according to a draft environmental impact statement that covers training and testing planned from 2014 to 2019. The Navy calculates the explosives could potentially kill more than 200 marine mammals a year.
The old Navy analysis - covering 2009-2013 - estimated the service might unintentionally cause injury or death to about 100 marine mammals in Hawaii and California, although no deaths have been reported.
The larger numbers are partially the result of the Navy's use of new research on marine mammal behavior and updated computer models that predict how sonar affects animals.
The Navy also expanded the scope of its study to include things like in-port sonar testing - something sailors have long done but wasn't analyzed in the Navy's last environmental impact statement. The analysis covers training and testing in waters between Hawaii and California for the first time as well.
The Navy isn't saying it will injure whales and dolphins as it trains sailors and tests equipment. It's telling the public and environmental regulators that its actions have the potential to harm or otherwise prompt a reaction in the animals.
The Navy takes a variety of measures to prevent harm to the animals, including turning off sonar when marine mammals are spotted nearby. It says the actual numbers of injured animals would be lower as a result.
The Navy must provide the information to the National Marine Fisheries Service to earn a permit for its activities.
The Navy uses sonar to track enemy submarines, torpedoes, mines and other potential threats underwater. Sonar operators send pulses of sound through the ocean and then listen for echoes from objects hit by the sound waves.
Scientists say the sound may disrupt the feeding patterns of marine mammals. The sound may also startle some species of whales, causing them to surface rapidly.
The Navy will be holding public meetings on the study in Hawaii during the week of June 11 and in Southern California on June 20.
The Associated Press contributed to this report.