IJustHadToLookHavingReadTheBook · Today 07:53
Is the banging likely to be them actually banging or some other sonar phenomenon from the vessel? Sorry if stupid question!
It's not a stupid question, not many people have any idea about the practicalities of sonar equipment. Any beacon, or other sonar device will operate at a defined frequency of sound, for a particular length of time; it may emit several pings over a specific time.
This will sound very different to someone banging.
It will also be different to the sounds of the wreck settling.
On a typical marine survey, we deploy a sparker, (loud, low frequency) a chirp, (medium frequency, just audible to the human ear) a side scan sonar, operating at high and very high frequency. All three have high frequency positioning beacons and we also use a single beam (high frequency) echo sounder and a multibeam echo sounder (high frequency).
All of these operate simultaneously. If, as the navy expert says, you can't discern one sound from another, we wouldn't be able to operate like that, never mind have a passive hydrophone receiver, to listen for whales and dolphins.