Bridge hangs in balance over dolphins' hearing

US scientists are eavesdropping on two pods of wayward dolphins to find out what they're hearing.

The researchers placed underwater microphones in a river near the New Jersey shore to record sounds that might be scaring the dolphins from heading back out to sea.

The recordings will be analyzed this week as scientist continue to monitor the estimated 12 bottlenose dolphins that have been feeding and frolicking in the Shrewsbury and Navesink rivers since the beginning of summer.