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Old 06-07-18, 08:25 AM   #1
greyrider
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Default Analyzing sound contacts for range with hydrophones

well, we all know how important the soundheads are to a submarine, especially when the submarine is submerged and under depth charge attack, they are the only sensor the submarine has to survive and defend itself against something like that, they are the eyes and ears of a submarine submerged below periscope depth. in this post i want to analyze the sound signal coming from a sound contact of shipping. we definitely can get alot of information with the hydrophones, if we know how to use it and what to look for when tracking or searching. id like to share some things i learned using the hydrophones over the years.


as far as the sounds coming into the headphones of hydrophones, in sh4 we only have 3 sounds, ambient, propeller, and engine sounds. in order to at least get a handle on estimating a range to target using the hydrophones, we would have to compare these sounds in relation to each other at ranges where a good abstract range can be estimated and plotted on a map. with a few more things , like a relative movement line, we would be in pretty good shape to tell where the contact is and where its going. using the same idea that made the sonabouy recordings of world war two, or alittle after, for the sonar school, i made a test mission, with the test ship starting beyond the listening radius of the hydrophones. you could say, why bother, we have radar, and then you could read clear the bridge and see in real life how many times the SJ burned out, how they took it all apart, and had all of the components on the conning tower floor, looking for the components that failed or burned out, replacing them, and then putting the SJ back together again. while it was getting repaired, tang would double the watch on the surface.

the test ship's course was made to start outside the listening radius, cross into it, and then steam right for the submarine, going right over it. the listening radius of the hydrophones is 18.3 nm. as it enters the listening radius, the three sounds, ambient, propeller, and engine sounds will be compared with one another as the range decreases, to try and identify certain ranges which would give a clue as to how far away the contact is.

i made comparisons every 10 minutes, until the target ship passed over head, the test ship is the iowa battleship, (i knew i would hear engines sounds from it), the iowa will travel 1.5nm in ten minutes, the results are below.

when the test ship crossed into the radius, it appears as an unknown, then identified as a warship by me, thats important for the ai sonarmen.

from the time the ship enters the listening radius, until it gets 1.5nm into the radius, (16.8 nm from the submarine.)

1.5nm in - 16.8 away

ambient amplitude is greater than propeller sounds, the ambient sound varies and sometimes sounds like a roaring hurricane, which masks a beat or two of the propellers, there is no engine sound at this range. the ai sonarman will respond to the command, "report contacts", when asked to follow target, will not respond. sound cone is a full 20 degrees. this is a good range to plot if you hear skipped or masked propeller beats (16.8nm) from submarine.

3.0nm in - 15.3nm from submarine

no change, ambient sound greater than propeller sound. very small increase in decibels of propeller sounds, no engine sound, ai sonar responds to "report contacts", will not respond to follow command.

4.5nm in - 13.8nm from submarine.

ambient sound greater than propeller sound, no engine sound, ai responds to report contact, will not respond to follow contact command.


6.0 nm in - 12.3nm from submarine

ambient sound greater than propeller sound, propeller sounds more crisp, clear, amplitude increasing, every beat can be heard, no masking of beats. no engine sound, ai responds to report contact, does not respond to follow contact.


so far, in the above ranges, theres not much to go on to get a good estimate of range, accept at 16.8nm and that the ai sonar cannot follow at these ranges, those are the only clues for these ranges.



7.5nm in - 10.8nm from submarine

ambient sound greater than propeller sound, propeller sound increasing, no engine sound, ai responds to report contact, ai responds to follow contact, begins following.

here is a good range to plot when the ai sonarman can follow contacts, (10.8nm) from submarine


8.17nm in - 10.13nm from submarine

faint engine noise, ambient sound greater than propeller sound, greater than engine sound, propeller sound greater than engine sound, ai sonar will respond to both report and follow commands. another good range to plot when engine sound detected. (10.13nm) from submarine




9nm in - 9.3nm from submarine

ambient sound greater than engine and propeller sounds, ai responds to commands



10.5nm in - 7.8nm from submarine

ambient sound and propeller sound equal in amplitude, engine sound less than both, ai responds


a good range here can be estimated when both ambient and propeller sound equal, (7.8nm) from submarine


12nm in - 6.3nm from submarine

propeller sound greater than ambient sound, ambient sound greater than engine sound, ai responds

another good range to estimate when propeller sound greater than ambient sound, (6.3nm) from submarine


13.5 nm in - 4.8nm from submarine

propellers the dominant sound, ambient greater than engine sound, ai responds


15nm in - 3.3nm from submarine

propellers the dominant sound, ambient greater than engine sound, ai responds


16.5nm in - 1.8nm from submarine

ambient sound cannot be heard, propeller sound completely dominates ambient sound, engine sound less than propeller sound, ai responds

another good range to estimate on the map (1.8nm) from submarine


18nm in - .3nm from submarine

propeller and engine noise only sounds in hydrophones, ambient sound gone, ai responds.


so there are about 6 good comparisons of sounds that will produce a range that could be plotted on a map, the ranges closest to the submarine help determine how close the escorts are when depth charging.

theres alot more to say about the hydrophones, tracking convoys by picking out one ship in the front row or by picking out one ship in the back of the convoy, and tracking that one ship, where it goes, the rest of the convoy goes to, determining relative movement, using the fringe bearings of the sound cone to determine direction..and more.
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Her gun crew had guts, however, for from her canting bow came a half dozen well-aimed rounds. How they pointed and trained their gun on that tilting platform will long remain a wonder, and their dedication in keeping up the fire until they went under would be a matter of pride to any nation.

O'Kane, Richard. Clear the Bridge!: The War Patrols of the U.S.S. Tang

Last edited by greyrider; 06-07-18 at 08:36 AM.
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Old 06-07-18, 08:41 AM   #2
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Very nice test greyrider. Thanks for that. Which mods (if any) did you use for your test? Do you feel adventurous enough to try it in a different game configuration?... - that's a lot to ask of a fellow, I know!
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Old 06-08-18, 09:57 AM   #3
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Quote:
Originally Posted by propbeanie View Post
Very nice test greyrider. Thanks for that. Which mods (if any) did you use for your test? Do you feel adventurous enough to try it in a different game configuration?... - that's a lot to ask of a fellow, I know!

ahoy Propbeanie......for your questions, i use trigger maru 2.5, otc for trigger,
but its not really a question of a mod, 18.3nm is the same radius of the listening range that was sh3, in that respect, sh3 and sh4 are the same, sh4 is sh3 in the pacific really, same map, same listening radius.


i do have every man qualified for the room, and i have taken some of the german special abilities and american special abilities, and have as many as possible qualified with one of them, the yellow abilities can be activated, i have alot of repair guys that can fix things pretty fast when they need to be activated, the passive ones add more range or whatever action of the ability gets improved. that wasnt a factor here tho, i did this before years ago, during my days with stock sh4 and sh3, so really theres no change, no mod i know that i used changed the sound radius, so i would say it doesnt matter what someone uses in mods, they wont have an effect, but if it was up to me, i'd have it as in rl, that it changed every day, sh4 does not model closing and going away sounds like in rl, they both the same, i have listened to both closing and going away, theres clearly a difference, we only know by asking ai. in the book clear the bridge, okane writes, as they were approaching a target, sonar caught the ship turning before the rest of the fire control party, because he heard the rudder moving, these types of sounds are not in the game, he said thats the difference between a listener, and a sonarman. anyway, i wouldnt worry about that tho, i dont think it will affect you, its hardcoded, probably becus underneath, its sh3



mods i use








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Her gun crew had guts, however, for from her canting bow came a half dozen well-aimed rounds. How they pointed and trained their gun on that tilting platform will long remain a wonder, and their dedication in keeping up the fire until they went under would be a matter of pride to any nation.

O'Kane, Richard. Clear the Bridge!: The War Patrols of the U.S.S. Tang

Last edited by greyrider; 06-08-18 at 10:08 AM.
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Old 06-08-18, 10:18 AM   #4
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Excellent. I really appreciate the time and effort you put into this for the community. We salute you!
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