Now they've not been able to re-acquire the signals, raising fears that the batteries have run out.
If what was heard was the wreckage and the batteries have ran out. At least you would think they know within a few square miles where it is.
Could be, or it could be much larger depending how many locations they caught the signal at. But even if it is a few square miles imagine going through a section of field with a flash light in the pitch dark looking for some small boxes, crazy.
I wish they would talk more about the science behind how they analyze the signal because there are quite a few variables to account for. I understand the basics, but what do they do for salinity, temperature gradients, and probably easiest increasing density with depth.