Hydrophone questions

[Pisces]

The low pass and high pass dials are filters to tune out certain frequency ranges. The low pass lets low frequencies pass, while attenuating/weaken the higher frequencies (squeaky/hissing) above the dial setting (in kHz, thousands Hertz) From 0 to the dial setting the amplitude of the sound is constant. Above that they get increasingly weaker. Similarly the high pass dial allows you to filter out low frequencies (rumbles) below the dial setting. Above the dial setting the frequency amplitude is constant, below it is increasingly weaker.

There is no real specific setting that needs to be set. If you have a lot of low frequency rumble and you want to pay attention to high pitch noises to identify sounds you turn up the high-pass a bit above 0. If you want to count the prop/shaft beat you lower the low-pass until you can follow it clearly.

Counting prop/shaft beats in skirmish doesn't work well to get actual speeds. As the devs somehow included a random element in it. Though you can tell if it speeds up or down. In workshop missions or tutorial world this prop/shaft beat relation is constant. But at all times, make sure you relate it to actual movement seen with the scope or other kind of measurements. Don't count on a formula for speed and later find out that the formula changed at some point.

[Aktungbby]

Bottom line then: I'll be attenuating my amplitude to arrive at the shaft beat !? Actually in one of the hydrophone sites I explored in response to the OP, the technique was particularly useful at 4000 meters using an accoustic Falke or ZaunKönig eel W/O needing the periscope...

[Pisces]

Except Zaunkönig and Falke don't exist in the game. Not the right years. No acoustic torpedoes in Wolfpack yet.

What I wrote is similar to the old treble and bass dials on your stereo/amplifier set.

[Bilge_Rat]

Thanks guys, all useful info.

Also found this on operation of WW2 Sonar. U.S., but same basic principle:

https://maritime.org/doc/fleetsub/sonar/index.htm

[John Pancoast]

May want to be careful using U.S. sub operations as a reference for Atlantic u-boat action.
Two completely different doctrines and equipment in two completely different theaters with different tactics, etc.
The German acoustic torpedoes were (mainly) to use against convoy escorts. While games allow it (along with ahistorical night periscope attacks), firing torpedoes via hydrophone use was not an sop for the Germans until the Type XXI came about................which was never used in combat.
Fwiw.

[Bilge_Rat]

The basic principles of sound propagation and detection in water are the same in the Pacific and Atlantic ocean...

[John Pancoast]

Originally Posted by Bilge_Rat

The basic principles of sound propagation and detection in water are the same in the Pacific and Atlantic ocean...

Good point.

[VonHoffman]

Originally Posted by Pisces

Counting prop/shaft beats in skirmish doesn't work well to get actual speeds. As the devs somehow included a random element in it. Though you can tell if it speeds up or down.

What do you mean "random element"? The prop RPM changes or the ship speed doesn't match?

There isn't a reason a way to derive the speed from prop RPM should change. For a given vessel, a certain RPM will give a certain speed.

[Pisces]

At the very least there is a difference between prop counts vs speed in the tutorial arena, skirmish mission and workshop missions. They cannot be transfered. I don't know if that is a static difference, or if it is dependant on the moment you decide to play one of them.