Thanks for all your comments - far too kind!
I'm just lucky to have extremely good reference material. I have to especially mention Ospreys "Anatomy of the Ship - The Battleship Bismarck" by Stefan Dramiński for that matter.
Really an excellent series of books, that I highly recommend.
Regarding heuhens question:
Bismarck was equipped with an array of active and passive Sonar systems:
1.)
The active S-Anlage (Schallanlage or Sonderfernsteueranlage?) was able to pick up a bearing up to a range of about 15.000m. Measuring accuracy was +/- 2°. (Source:"Schlachtschiff Bismarck Teil 2: Das wahre Gesicht eines Schiffes" by Malte Gaack & Ward Carr)
2.)
The NHG was a single hydrophone to detect Torpedo noises. Range is unknown to me, but the name "Nahbereich" literally suggests it was used to cover closer ranges. (Source: "Anatomy of the Ship - The Battleship Bismarck" by Stefan Dramiński)
In the above mentioned book by Malte Gaack & Ward Carr, the NHG is listed as a "navigational hydrophone".
Edit:
Found some interesting bits regarding the NHG in a thread on the extremely knowledgeable "forum marinearchiv"(
https://www.forum-marinearchiv.de/smf/i ... nowap.html note: its in German)
Quick Google translate:
"The NHG "Navigation listening device" was the code name for a device that basically worked like the GHG. However, its frequency response was tuned to the much faster-running torpedo propellers, which produced a brighter tone. Thus, incoming torpedoes could be identified and tracked independently of the GHG. The microphones required for this were installed in Dept. XXI. The NHG 38 device, also manufactured by the Bremer Atlas-Werke, h
ad a range of up to 2 km and only provided a rough bearing."
3.)
Bismarck also featured an echo sounding system that used a 22khz accoustic signal for depth measuring.
4.)
Regarding the Gruppenhorchgerät (GHG) I quote
http://www.kbismarck.com/controltiri.html:
"The Bismarck was also equipped with two sets of hydrophones for passive underwater listening. The Germans called these installations Gruppenhorchgerät (GHG), and consisted of two panels of 60 microphones, one on each side of the ship's hull. The maximum effective range was 26-40 km depending on conditions such as water conductivity and background noise. Tests conducted in the Baltic Sea didn't give very satisfactory results because of heavy background noise and poor conduction properties. However, in the deep cold waters of the North Atlantic under favourable conditions, bearings with an accuracy of 1 degree could be expected at speeds of 30 knots from a distance of 30,000 meters (32,823 yards)."
Of interest might also be this link:
http://www.bismarck-class.dk/bismarck_c ... g/ghg.html
cheers!
maomatic