Sank my first ship today with a vector analysis/hydropohone method like the one you described in your video. Awesome!
I realized that the hydrophone contacts are covering a (fixed?) +10 and -10 degree field. That means when the target bearing is e.g. 24° you can hear it anywhere between 14° and 34 ° (indicated by the green light on the hydrophone). As my aiming bearing was 14° I listened for the ship at 4° and waited for the green light on the hydrophone to go on.
Once the lamp lit up and I heard the merchant I switched to the torpedo controls and launched one torpedo "blindly" meaning without any visual contact. And it hit and sank the merchant!
However,this is harder than using an optical indicator, simply because you will lose precious seconds switching through the different menues
Still, I will use it in cases where i do not dare to raise the periscope.
Thanks again!
Btw, I discovered that one can use the middle mouse button to turn the hydrophone. Not sure if that is generally known.