In the Stock version of the game, you will get a ~lot~ of "Contact Reports". There is a setting in each group or ship that the game generates, to control how often, if at all that the unit will be reported on, and how long it will take for it to do so. For the most part, it's an exercise in frustration to try to track them down. However, they do give you an idea of where the known traffic lanes are. Unless something is rather close to you, there really isn't any sense in chasing "rabbits", because they do not keep the same course all the way across the ocean. Consider the reports as one of the game's attempt at "immersion", with the report coming across the radio from "Ultra", and your crew "plotting" them on the map for you.
In the meantime, sonar is difficult to plot or target with. It can be done, but you'll need to make multiple readings at evenly timed intervals (5-10 minutes apart) and "chart" them on the map (draw a line from your sub along the hydrophone's line). From that, you can somewhat get a general direction of travel, based upon the distance traveled on your map against the reported "speed" (Slow, Medium, Fast). I cannot recall those speeds' amount, so someone else would have to post with them...
However, you don't really know the distance, and the game will at times give you a sonar contact miles and miles away. When they say "Long Range", that means over 5,000 yards, but it might be 35nm also... Consider those long distances a "simulation" of the transduction of sound waves, and the clarity of the water you're in. More immersion...
It can take a long time to catch a potential target with hydrophone readings (besides possibly burning all your reserve fuel). As for using active sonar ("pinging"), there is a limit to how far out that will reach, even if you are accurate with the line you send the ping on. I do not recall it's maximum range, or if it's even notated anywhere.
Patience is key though, and it can be an exercise in frustration (I'm worn-out from all of this "exercising" stuff) to discover that the "target" you've been chasing / tracking for the last few hours is nothing more than a couple of sub-chasers with multiple sidethowers each, just "baiting" you for an attack...
You could try
which is found in Rockin Robbin's
Sub Skipper's Bag of Tricks 