The U.S. Navy wants to expand its use of a new low-frequency sonar, but there are indications this sonar kills whales and other marine mammals.

If the government approves the Navy's request, the decision will not be revisited for five years. The National Oceanic and Atmospheric Administration said Tuesday that low-frequency sonar would have a "negligible impact" on marine mammals.

However, when the sonar was tested in U.S. waters in 2003, several porpoises washed up on the coastline soon after. According to the Center for Whale Research, low-frequency sonar can cause bleeding in the ears and brain of marine mammals.

The new sonar has a much greater range than mid-frequency sonar, which the Navy usually employs. Marine mammals hundreds of miles away can be affected by low-frequency sonar, often losing their ability to track prey or communicate with one another.

The government's proposal to allow expanded use of the sonar is open to public comments -- but only through July 24. Public comment periods usually run 60 to 90 days.

Those who wish to comment on the proposal can do so by using the identifier "062206A" when contacting PR1.062306A@noaa.gov or visiting the Federal Rulemaking Portal at http://www.regulations.gov.