Hydro detection, a question

[lumat83]

Hi all

I've read on www.Uboat.net :

If a submarine speed was 4 knots, the submarine's underwater sound detector average distance of detecting another object was:

- for a destroyer- 5 to 10 nautical miles,
- for a cargo ship- 3.5 to 7.5 nautical miles,
- for a convoy- up to 50 nautical miles.

It seem that thoses distance are very different in SH3 (25kms maxi I thonk but for one contact). No ?

[el_Salmon]

I think this depends on bearing, because hidrophone has a directional beam.

[panthercules]

Originally Posted by lumat83

Hi all

I've read on www.Uboat.net :

If a submarine speed was 4 knots, the submarine's underwater sound detector average distance of detecting another object was:

- for a destroyer- 5 to 10 nautical miles,
- for a cargo ship- 3.5 to 7.5 nautical miles,
- for a convoy- up to 50 nautical miles.

It seem that thoses distance are very different in SH3 (25kms maxi I thonk but for one contact). No ?

I suppose that this might have something to do with the masking noise being made by the U-boat's motors - if you're at all-stop in SH3, then you can hear much further than the distances you mention above, but if you were trying to hear those ships over the noise of your own motors while going 4knots, then it wouldn't surprise me if the sound-spotting distances dropped down close to what you list above (I always listen at all-stop so I can't say for sure what SH3's distances would be at 4knots).

[Nedlam]

Originally Posted by el_Salmon

I think this depends on bearing, because hidrophone has a directional beam.

Is that why my SO always loses contact when I turn to head to it? It never fails at contact bearing 003 to 357 I stop getting reports and then get a message of contact lost.

I'll admit sometimes I get lazy and just want my SO to do the tracking for me.

[el_Salmon]

Is that why my SO always loses contact when I turn to head to it? It never fails at contact bearing 003 to 357 I stop getting reports and then get a message of contact lost.

Maybe with this picture it would be more clear

Originally Posted by el_Salmon

Maybe with this picture it would be more clear

lumat83 is talking about Hydrophones, NOT Sonar. Hydrophones are a PASSIVE device, Sonar is an ACTIVE device.

In simple terms
Hydrophone - very sensitive mike
Sonar - Very directional speaker (beam)

You listen with a Hydrophone to any noise source.
You "Ping" a target with sonar to get a return "Pong" on the Hydrophone to determine the range.

A Hydrophone does NOT make a sound beam, Sonar does.

Hydrophones can be inhibited by your own prop wash and your hull (depends where the hydrophones are mounted), also in RL by land mass. However land mass is not modeled in as an inhibiting factor in SH3.

[Serverdaemon]

Originally Posted by el_Salmon

I think this depends on bearing, because hidrophone has a directional beam.

The early hydrophones were fixed, but you soon get to purchase the 360 degree rotating improved model (That's the little "T" shaped device on the deck on the front of your boat).

BTW, "Sonar" is a generic term for using sound to detect other ships and submerged contacts while underwater. There is an "Active" variety and a "Passive" one. Active sonar sends out a ping, passive just listens.

S

[Nedlam]

Sorry for the confusion. I was talking about hydrophones. I honestly don't know what version of listening device lumat83 was talking about.

[lumat83]

Thank for your help, but when my hydro officer say for example : "contact 090 long range" what I an understand : the contact is at 10000 meters ? 25000 meters ?.
This was my question in fact. Perhaps it is depending to the weather conditions ? Or to the officer experience ? I don't know really.

Anybody know this for the new mods RUB and IUB ?

[Trav_R]

When the SO says "long range" that can be as little as 5,000m on up to 20km or more. You can't plot anything on the map based on his estimate of "long range." You'd have to listen yourself. He doesn't start saying "medium range" until the target is pretty damn close, like 4-5k meters or so.

[Twelvefield]

And if it's short range, prepare to trade paint with your target.

[lumat83]

Ok, thanks for your responses

But it's difficult for me to estimate if the contact is in approach or not and how near is it

[Wolfram]

Originally Posted by lumat83

Ok, thanks for your responses

But it's difficult for me to estimate if the contact is in approach or not and how near is it

I turn up the volume and follow him for a few minutes, then I like to surface if he sounds faint enough. Then I go racing on surface at off angle (not direct) to my estimated direction hmm not a full 90 usually about 20 to 30 for a few minutes then submerge if contact gets weaker I know I miss calculated.

If close enough lock on with operator and track him more to refine the direction/angle.

Sorry not a lecture just how it been working for me so far.

Have Fun!