One thing to consider if you sense a lack of obvious sonar contacts is the personell presently at job at the the sonar/radio stations. If these are tired, or not specialists, they might not give you a feedback at all. Even when you request it specifically. It is a good thing to designate special sonar operators. My priority for these designations (only one additional per performed mission) is torpedo (reloading time), machinist (to move at all) and sonar. You get better performance if you let the officers qualify first. Of course, in SH3 Commander you can get around this by adding such specialities freely to the whole crew. Which some might find a little "cheety".....
Also, to designate repair specialists can be very rewarding. It makes wonders when you get hit to have a good repair crew. Has saved me a lot of times.....