the only way I could see this working is if the target is heading towards you for the most part.
For example, if you take a few bearings and determine that the target is moving from your port to your starboard then start moving towards the sound contact and to your starboard. Keep doing this and taking bearings until the bearing readings become static. This would indicate that the target is coming directly at you (or perhaps going away) Once you determine that the target is coming directly at you with no change in bearing (and you are not moving) then you know its course. There are a lot of "IF"s in there though. The target has to already be heading towards you and you have to be lucky enough to get right into the path of it and stop.
Just theorizing.
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