Here are the Sonar.wav files of all the sonars (asdic) sounds encountered in the supermods of sh3 :
-stock sh3
-ccom12
-nygm3
-gwx3
-wac5.2
-lsh2020
-gwxonealex1.39
-gwr21
Sh3 sonar sounds :
https://www.dropbox.com/s/5hlcck5eq4...sounds.7z?dl=1
Just rename the one you prefer by Sonar.wav and copy it to paste into data\Sound from your Sh3 installation to have the same in your game :-)
Ping ping ^^
What is the most real sonar sound for you ?