"Pardon me if this has been discussed - I gave up reading this thread midway due to so much uninformed speculation - but iirc from the AF447 threads an acoustic wave can be bent as it passes through the interface between media of different density (e.g. layers of different temperature) and thus peak detection would occur when the receiver was not directly overhead the source. "
thats deflection is correct, but nevertheless the range of this device is only few kilometers at all. 10 kilometers radius ( so more than the pinger range ) have been scanned by bluefin and nothing - not even some sunk debries beyond the main wreckage - was found.
that due to my understanding cannot be and one statement ( pings are from an ulb ) excludes the other . ( bluefind scanned the bottom around the ping and nothing was found )
so like said either the origin of the pings was something else or bluefin did not scanned every piece of the bottom in the 10 km radius , maybe due to depth limitation .