How do you detect surface ship at long range?

[Dron22]

I assumed that because of the noise a ship's screws emit, it should be easy for sensors on a submarine to hear a ship from far away. However I find that I have to get close within 5nm to detect a ship on the broadband sonar display. Of course it's easy to detect a ship from far away when it's constantly ping it's active sonar, but what do you do if it's not?