Hydrophone Distance Estimation

[ChrisPhoenix]

Greetings fellow Kaleuns!

I am trying to become a better hydrophone operator. So i was wondering if there is any "rule of thumb" or anything like "a gain of 3 means around 5000m". Basically i am looking for a quick but simple way to estimate the distance to the target as accurate as possible but in the shortest amound of time. Methods like the four bearings-method are never used in our missions. So maybe you guys can help me out with your experience?

thanks in advance!

Chris Phoenix

[Pisces]

You might want to search the WP discord server. There have been plenty rules of thumb postulated for that. But the problem is, different unit might have different source levels. So you might think X gain is Y far, but it could actually be further or closer. That's why I don't bother. It's also not that neccesary. Just point the bow at the sound and go full speed on the surface. They will appear soon enough out of the mist.

[Superesse]

Regarding steaming towards the convoy and finally they appear. Doesn’t that only work in clear weather or slightly cloudy (I don’t remember the terms)? If it’s foggy you cannot do that, right? Because you won’t see the convoy until you’re dangerously close? I’ve never tried fog yet, so it’s just a guess.

About distance checking. I am poor at it myself. But I think you need to be close enough to distinguish a single ship, then count the propeller rotational speed (because I assume that affects sound level?) and then based on the combination of gain and propeller speed calculate the distance (I don’t know how). This is only my guess.

[Lost At Sea]

I would also love to know how to do that!
By the time I managed to fumble my way through the four bearings-method the convoy has usually reached Rio de Janeiro... :doh:

Cheers,
Lost

[ChrisPhoenix]

The Discord Channel is a little messy in terms of finding information in my opinion. I rejoined it, read thourgh some stuff but hard to find anything. There is just too much going on.

Just heading towards the convoy is fine for the most situations sure, but i would also like to be able to know if a destroyer is at safe distance to surface by just relying on the hydrophone for example.

Of course i don't want to say "alright contact is exactly 5435m away." But plus or minus a 1000 meters would be nice to know.

[Pisces]

It should be safe if you do a periscope check before you surface. Should be standard procedure anyway.

Yes, discord is messy. But you should be able to search the channels for keywords. Rule seems to fit as one.

[ChrisPhoenix]

I didn't know you could do that. :o That actually helps a lot! Thank you.

[Pisces]

As for foggy conditions, yeah, you better be on your toes and pay attention. Make sure the deck-watch is doing it's job. Either slow down and turn away at the first sight, or immediately dive. Or both. Or don't go fast in the first place. Oh heck, do all to be sure.
:Kaleun_Wink:

[Superesse]

Slow down AND dive is not a good idea, right? 😁

[Pisces]

Dive might take longer as you slow down, but you don't decrease distance as much either. At 18 knots you move 9.36m per second. Also, if you can retreat into the fog again, you stand a better chance of escaping than being submerged (until radar becomes a thing)

[ChrisPhoenix]

I actually picked up some things from Discord now. I have yet to test them tho. Regarding distance to destroyers: i'd rather not stick my periscope out if i'm not 100% sure he is far enough away. That's why i'm trying to do it with hydrophone. Better stay deep...

Regarding Diving speed: I only go full speed while diving when the alarm bell rings. Which is only when we are spotted at the moment. Copied that from Silent hunter, where alarm automatically meant full speed. In any other situation i'd rather dive slowly, because it is much easier to stabilise the boat when you do it slower. Going full speed and maintain periscope depth is rather hard.

[Pisces]

If the direction to the destroyer is not moving you can be reasonable assured it is far away (or still homing in to you ;) ). If it drifts noticeably in degrees while you are listening, then it is probably quite close. And if you don't pop your periscope too high (just crossing the waterlevel, still in the waves) then you should be able to see it's smoke and know you should be on your guard.

For crash dives you also better have your negative tank filled beforehand. I never said you should stay at full throttle. Once you are under you are clear and can do whatever you think is needed. Just be sure to leave halve of a tick in the negative tank, as that puts you better neutrally buoyant. (That is, until next week as they are bugfixing buoyancy stuff they said. So next weekend all could be new again.)

[ChrisPhoenix]

Yes the boyancy update will most likely change everything. And i personally can't wait because i am waiting for a trim tank since the very beginning...

I also hope they add rough seas and make the boat a little more shaky in the water. But the trim tank alone will make this update awesome.

[Fanders]

Hi everyone!

I just did some data collection with the hydrophone in tutorial mode (where you can se the other ships distance and bearing on the map).
I focused the hydrophone in the exact vector to the target, then I turned the gain knob to the point that the sound turned into distorsion. At that point I collected the distance of the target from the map.

I plotted the data in google sheets and found out that the relationship between the gain and the distance is linear.
Thats quite strange btw, because the sound preassure should decrease with the square of the distance.

One more thing that was a bit strange is that gain level of 2 seems to be the limit. There was no point lowering the gain below 2 -no matter how close i got to the target.

Anyway,

from the data colleced i managed to make a trendline/regression curve of the plot. In my website below you can download the pdf of the diagram i did and use if you want!

Of course this could be done with more precision, but i think its a good diagram to use for rough estimations!

:ping:

www.gnomon.se

[PeterS]

Thanks for your work on this! What were your settings for high and low pass filters? I suppose these need to be identitcal to compare the results with your diagram.

Personally I found 1 and 8 pretty reasonable filter settings.

[ChrisPhoenix]

Thank you Fanders! That was exactly what i was looking for. I Can't wait to test that out.

[Fanders]

Relevant question! :Kaleun_Wink:

My settings of the high and low pass filters was at the deaufult level:

High Pass - o khz (clockwise maximum)
Low Pass - 22 khz (counter clockwise maximum)

[stellaferox]

Hi everyone!

I just did some data collection with the hydrophone in tutorial mode (where you can se the other ships distance and bearing on the map).
I focused the hydrophone in the exact vector to the target, then I turned the gain knob to the point that the sound turned into distorsion. At that point I collected the distance of the target from the map.

I plotted the data in google sheets and found out that the relationship between the gain and the distance is linear.
Thats quite strange btw, because the sound preassure should decrease with the square of the distance.

One more thing that was a bit strange is that gain level of 2 seems to be the limit. There was no point lowering the gain below 2 -no matter how close i got to the target.

Anyway,

from the data colleced i managed to make a trendline/regression curve of the plot. In my website below you can download the pdf of the diagram i did and use if you want!

Of course this could be done with more precision, but i think its a good diagram to use for rough estimations!

:ping:

www.gnomon.se

Hi Fanders,

Would you mind sharing the mathematical equation resulting in that line? From the graph I get something like Y = 5555.55 * X - 10833.33 (meter) right? Or in hm Y = 55.55 * X - 108.33

[Fanders]

Of course!

The linear equation for the trendline is:

y=5273x-9656

[Kermit the Frog]

Ok Here's what i have:

Tutorial,
we'll start out with a basic setup. High/low pass rotated to the right, gain at about 1-2.

We hear a contacts, but they're very "wide", it's almost impossible to give a precise bearing.

1. slowly raise "gain" level. At some point your contact rapidly becomes louder. Stop immediately.

2.
hight pass - will help us to isolate engine/screw sound
low pass - will help to isolate asdic source.

(i am not sure if it shall work like that but it's how it works right now).

3.
Rotate "High pass" a littlebit to the left - 2 points will do.

4. now check your contact how it "behaves" if you're rotating from side to side it shall sound like this "thumbthumbthumbthumb - HRKSZRKSZ - thumbthumbthumbthumb" you shall have an area where your contact sounds like very loud, broken radio.

5. Turn "high pass" more to the left and adjust "gain" accordingly: if you can't hear "broken radio" type of noise right in the middle, add some more "Gain" lvel and scan again. if "broken radio" is to wide - lower "gain" level.

6. Now you narrowed you contact to 2-3 deg. Bravo! You have precise bearing. ( in tutorial i reached precise bearing for "High pass " set about 12-14)

7. if your contact suddenly stops making "broken radio" type of noises it means that he's moving away, and you have just discovered it. Report to the commander! contact, bearing XX, moving Away. A "Gain" level will give you quite good info about how far is your contact, and if he's moving away, or getting closer.

Good luck!

[VonHoffman]

A method I use to center a contact is to look for where the "ends" of the sound are (where it fades out completely and I can no longer hear it). The contact is in the center.

When dealing with a convoy at distance, I use this method to discover which way the convoy is moving before I move to intercept. I head for the quiet end of the sound in the forward direction of the convoy, as it will take me some time to get there, putting me ahead of the convoy where I can wait...

The "width" of the sound tells me if they are getting closer or moving away. The wider the spread, the closer the convoy/ship.

I like the idea of using the training mode for learning the ranging with the hydrophone! I will give this a try later!

[Captain Adonis]

so I watched a youtube video and the guy said take your gain level, and that is a guess, times 5 minus 8.5 and that is your range. Example gain is 2.2
2.2*5-8.5=2.5 then times 1000 for a range of 2500 meters
I have not tested this fully

https://youtu.be/kwRaZ3RmQb0

[Pisces]

There will be changes how the hydrophone station and it's gain works in the newer versions (not yet released) So I would not count too much on learning that rule of thumb.

Besides, that range doesn't tell you much. You know where it is, so just head there until you see something of it. The convoy is large enough so you won't miss it. Then consider how best to maneuvre to get visual data. Turn away to not get closer initially 'as you get your bearings' on what to do. You want to focus on speed and angle on bow (or something giving their course away). Range doesn't help you much when the torpedoes will leave your tubes and head straight away. It only helps in telling you when the impact is likely to occur. That is, if speed and AOB was correct to begin with. Otherwise it is a likely miss. Range is just a minor input to a correction for when the torpedo makes a turn towards the target.It is also a value for the torpedo salvo spread calculation if you decide to use that.

[Kralizec]

When you are on the right bearing, the sound disappears at exactly 5000m for each gain step. Gain 1: 5000m, Gain 2: 10000m and so on.

I use this to measure the distance. In most cases it works better than trying to use overdrive when ranging the closest ship.

From this gain setting, you can turn it up 1.5-1.7 gain steps before the sound starts clipping. This is more subjective so less accurate. Onset of clipping is different depending on the type of ship so you won't get the best result, but on the other hand, you can get an accurate bearing at the same time.

So a ship at 5000m distance:
- sound will disappear at 1 gain
- sound will go into overdrive at around 2.5 - 2.7 gain

You can turn it around:
- the sound disappeared at 0.4 gain
- distorts at 1.9 - 2.1
Distance is 2000m

[Kralizec]

kamini982:Kaleun_Salute:

Do you think it would be possible to reduce the number these types of comments? It takes up so much space and contributes nothing, while reducing the signal to noise ratio of every single thread on subsim

[Aktungbby]

yes sir you are right.......:salute: No doubt thru trial and error:arrgh!:

[karamaujlay]

The Discord Channel is a little messy in terms of finding information in my opinion. I rejoined it, read thourgh some stuff but hard to find anything. There is just too much going on.

[Aktungbby]

The Discord Channel is a little messy in terms of finding information in my opinion. I rejoined it, read thourgh some stuff but hard to find anything. There is just too much going on. karamaujlay!:Kaleun_Salute: