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But good point with the measuring the depth: Will this always be heard of the destroyers when in range or only when they are alertet? And how far is the range? Sure I can find it out slowly ingame but a rough estimate again is always helpful

Some useful info here: http://jproc.ca/sari/asd_et1.html Bottom line: the effective range is 2000 yards BUT the ASDIC's individual operator is the judge of how deep you are..' "A smart submarine commander, with a lot a nerve, would head into the area of the depth charge explosions. He knew, that within this area, nothing could be identified on Asdic for five to ten minutes, especially if the charges had been rigged for detonation at 250 to 500 feet. A safe shelter could be had even if it was only temporary." "While in convoy, operators used Asdic to listen to the engines and propellers of other ships which was very helpful during fog conditions or on nights when everything was pitch black. To say that convoys were well protected by Asdic would be an understatement especially in the early years of the war. Typically, a convoy consisting of 30 to 50 merchant ships created a perimeter distance of 16 to 18 miles. In theory, the escorts were positioned so that their Asdic beams overlapped, providing unbroken coverage of the convoy perimeter. The reality of the situation was different. An escort group usually consisted of one destroyer and three of four corvettes, barely enough to provide proper coverage especially with Asdic whose range limits averaged around 2000 yards under normal conditions. When convoys did have sufficient escorts, not all the Asdic sets were used simultaneously. If two ships were operating in the same area and on the same frequency, there were two options. The primary option would mean shutting down one of the Asdics." IN short: as with the radar that the battleship Bismarck's commander famously and erroneously assumed was giving away his position because it was audible TO HIM but not being received back accurately by the transmitting vessel, Sonar is dependent on the vagaries of water and background sounds, tidal rips and temperature gradients, and the operator may not be receiving an accurate reverberation of the signal 'bounceback' You, in the sub, can (always) hear his sonar; but that doesn't mean the enemy operator (the HSD) is receiving or 'interpreting' his signal correctly especially with a type 123 or 123A asdic sets as on most corvettes for example. Whether the SHV/III games reflects a particular type of ASDIC equipment or the vagaries of a sonar operator and/or water and previous depth charge disruption in the game is unknown to me.