Corrections to Sound Levels on Various subs

[CV60LCC19]

DB Selector

Both

Affected DBID(s)

Various

Summary of Changes

I know this entry isn't "according to Hoyle", but I wanted to present the spreadsheet I'm beginning to fill out to evaluate the data on submarine sound levels. It is not complete, but I wanted some comment on it. I'm doing it as a spreadsheet, with a second tab for including source material from books. I'm including data on the displacement, number of screws, double/single hull and country, and year in commission to help in interpolating data when we don't have good sources. I have the source for the data as a note in the applicable data cell. I have 3 columns for VLF frequency data, as sometimes I have 3 data sources, so that will allow us to compare the data. Is this format clear and useful? Is there anything I should change?

Sources

See attached Sound of submarine.xlsx .

[PygmalionOfCyprus]

This is good. Real good. I'm going to pin this for the duration so that others can contribute if they have anything to add.

I'll also look at making some backend schema changes to allow for sub-specific signature settings; we have the option for aircraft but not submarines for some reason. I'll then be able to set specific sub signatures rather than merely assigning generic modifiers.

[PygmalionOfCyprus]

Can I close #1832 and #1739, as they're basically included in this project?

[CV60LCC19]

Yes, go ahead and close 1832 and 1739. I'm also thinking about adding columns for shrouded props, skewed 7 props, and tiles, Because these have fairly significant effects on sound. Here is an idea: Once the spreadsheet is developed a little bit more, posting it on the forums for comment, as we will probably get more input there than here, and some of the people on the forums have real world acoustic experience, vice myself. Although I was a SWO, my ASW experience is more limited, so expert opinion may be helpful.

[CV60LCC19]

One other question: How do the generic modifiers work in the game? Right now, I'm taking the Sound Level data "as is", but there is a wide variety. For instance, some data is on submarines at PD and 6 knots (where there would be some cavitation), while others is at PD and 4 knots (with minimal cavitation). Some is on diesel and some is on battery. I have data that would allow me to reasonably interprolate some information from here, but I wanted to try to standardize the data on this sheet with what the game uses. We may want to get together via Zoom and/or a phone call to coordinate some of these issues. I'm CV60 on the forums. If coordination sounds like a good idea, PM me, and we can arrange a call.

[CV60LCC19]

Yes-go ahead and close it.

[CV60LCC19]

Here's an update to the spreadsheet. I've added more references in the second tab, a couple of more columns for assistance in interpolating the data, and a few more data points on various sub classes. Plus, I've color coded some of the cells to denote when we have interpolated the sound levels, and for when the sound level is a discrete frequency, as this will establish the minimal sound level for the class. (sometimes the only data is for a discrete frequency, so while not ideal, it is still useful information for interprolation.) Sound Levels of Submarines.xlsx .

[smcclaire]

Hi CVN60 -- I'm one of the developers working on Command and I've been looking into updating the sonar model. Dimitris pointed me your way after he received your recent forum PM. The submarine noise data will also be helpful verifying the sonar model, so thanks for providing it.

Dimitris mentioned you had reference values for ambient ocean noise levels? If you can provide these (perhaps on another page in the same spreadsheet?) for our frequency ranges (200 Hz, 3kHz, 7.5kHz, 20KHz) that would be much appreciated.

[CV60LCC19]

I will get you some data. It may take a couple of days. FYI, here is the latest submarine noise info. There are a lot of gaps in the data, but I think we have enough that we can begin making informed guesses on many of the classes.

[PygmalionOfCyprus]

(I don't think the attachments go through on email replies -- any chance of an edit to the comment above to include the latest info?)

[CV60LCC19]

No problem. Here is the latest revised spreadsheet. I still have a lot of work to do, but I think it is starting to become a useful tool for documenting and interpolating sound levels of submarines. Regarding ocean noise levels. There is no global mapping of noise levels. See https://www.nature.com/articles/d41586-019-01098-6#:~:text=There%20is%20no%20global%20map,calculated%20on%20a%20logarithmic%20scale). However I've collected a variety of peer reviewed sources that have mapped various locations that will allow us to make educated guesses for much, if not all of the globe. In the alternative, we can use models such as this (see attached, from " Design and simulation of a new model for shallow water multipath acoustic channel in the Persian Gulf" at https://www.researchgate.net/publication/241180813_Design_and_simulation_of_a_new_model_for_shallow_water_multipath_acoustic_channel_in_the_Persian_Gulf/download) to generate noise levels in game based on ship traffic levels (possibly using AIS data to get approximate level of ship traffic) and the scenario wind speed/sea state settings. This would give pretty good approximations (when adjusted for water depth) of the ambient noise. Let me know if you 1) want me to piece the global data together (which may actually be useful for testing the model you chose) or 2) if you just want a possible model of coastal and ocean noise levels based on depth, wind speed and traffic levels Sound Levels of Submarines-2.xlsx

[CV60LCC19]

Hi CVN60 -- I'm one of the developers working on Command and I've been looking into updating the sonar model. Dimitris pointed me your way after he received your recent forum PM. The submarine noise data will also be helpful verifying the sonar model, so thanks for providing it.

Dimitris mentioned you had reference values for ambient ocean noise levels? If you can provide these (perhaps on another page in the same spreadsheet?) for our frequency ranges (200 Hz, 3kHz, 7.5kHz, 20KHz) that would be much appreciated.

PygmalionOfCyprus and Smcclaire: I'm grinding through various scientific reports and getting the data you requested. However, I think it would be very helpful if I could speak to you regarding what you want and need, and the best way to get that info to you in a way that is easy to understand. Basically, there is a danger that I am going to spend a lot of time gathering data that isn't much use to you. Hence, speaking to you would be helpful in my research and presentation. The basic question revolves around several issues: 1) The Bandwidth for oceanic noise in the game is possibly too broad. The vast amount of noise used for ASW is below 5KHz, with the overwhelming amount of the passive ASW work over the past 100 years being done in the .01-2 KHz bands. In contrast, the game has bands for up to 500 KHz. In other words, I don't know that data in the 5-500 KHz bands even exists, as I believe there are relatively few ASW/oceanic sound sources of any military interest in those ranges ; 2) there is a wide number of variables that go into determining the sound levels of a particular patch of ocean, including wind/wave/rain, man made sources, such as maritime traffic and oil exploration, seasonal sources such as ice packs and hydrological factors such as water depth.

This is a long winded way of me saying that it would be helpful for gathering the data you need to understand how you are planning on establishing noise levels in the game. What I would suggest might be for the game to establish traffic levels for discrete areas of the ocean, using AIS data, and then approximating man-made noise levels based on this level of traffic. Additional decibels could then be added for depth of water (shallower is louder, due to reflection), weather conditions and the presence of pack ice. Scenario designers could then modify the generated value by either placing of biologics or via the date of the scenario, as noise levels have been increasing since WWII. If this is the method you would use, then what I need to do is to not find data on individual areas of the ocean, but find data to help you model it, with possibly sound information levels on discrete areas so you can validate your model. In any case, it would greatly assist me in discussing these issues with you so I can improve my data collection activities. Can you PM me in the Matrix Forums, and we set up a Zoom meeting to go over your data needs, and review what I have thus far, so I can make adjustments in my data collection? I am CV60 in the Matrix forums.

On a slightly related point, I've added some additional info to the submarine noise level excel sheet. It is a new reference that adds some SS/SSK information, and is located on the second tab.
Sound Levels of Submarines-2.xlsx

[PygmalionOfCyprus]

Sorry I've been taking so long to respond to you on this: I've been doing my best "chicken with its head cut off" impression these past few weeks. I'll speak with Steve and look to arrange something.

[smcclaire]

Hi CV60LCC19

First off, thank you very much for what you've provided already. For my part, I don't need specific data points for individual subs (though I am sure Ethan will be happy to have them!) so much as general confirmation of some assumptions in Command's sonar model. Specifically:

1) Ambient noise at 200 Hz (Command's lowest frequency) is dominated by shipping noise while our other sonar bands (3-20kHz) are all dominated by sea state related ocean noise.

2) A ballpark value for shipping ambient noise is about 50-70dB at 200Hz depending on the amount of shipping in the area.

3) A ballpark value for sea state ambient noise is about 45dB at 3kHz at sea state 1 and goes up about +10dB every time sea state increases by 3 (i.e. 55 at sea state 3, 65 at sea state 6, assuming the same frequency of 3kHz)

4) The general noise level of submarines matches the numbers given by the Miasnikov reference you posted (https://spp.fas.org/eprint/snf03221.htm) and (most importantly) these numbers are ultra-quiet / minimum noise level, not maximum noise level at full speed.

If you have data that is significantly different than any of the four assumptions above, then that would help me catch potential problems with the model.

This is a secondary project for me at the moment, so there is no huge time pressure. I'm happy to chat on Zoom or other voice if that is still helpful for you. Let me know what day/times you're available and we can arrange something if so.

[CV60LCC19]

smclaire-Here is a graph from 1954 which shows a generalized db level vs. frequency done by Bell labs which may be useful. (source: https://asa.scitation.org/doi/suppl/10.1121/10.0005430) I am working on a write up that will pull all this together. Based on graphs like this, one of the problems we have (IMHO) in the acoustic model in CMO is that the acoustic bands used in the game are too broad. a 1-20, 20-50, 50-100, 100-200, 200-1000, 1000-10000 Hz model may be a better fit for modeling militarily useful/significant oceanic sound levels.

[CV60LCC19]

PygmalionOfCyprus- Here's the updated submarine sound level table. I believe the numbers in highlighted in green are pretty good "max quiet" numbers, as they are taken from formerly classified US government databases. In most cases, I've adjusted the numbers to account for cavitation, because many of the US government numbers were for targets traveling at 7 knots. Using cavitation tables, I believe a -10db reduction is appropriate for 1 or 2nd generation submarines, to get sound levels at a uniform 4 knots. I've noted in the notes contained in each cell where I have made this adjustment and how much was made. For reference, the adjustment is based off of figure A6-3 in Stefanick, "Strategic ASW and Naval Strategy" The numbers in green also seem to be supported up by the numbers given in Stefanick.

My plan moving forward is to now use the relative noise levels in the ONI tables that are attached as "Tab 2" to the spreadsheet to estimate the sound levels of the remaining submarines on the list. Please let me know if you have any questions/comments regarding my data and methodolgy. Sound Levels of Submarines-2 DRAFT.xlsx

[CV60LCC19]

Sound Levels of Submarines-3 DRAFT.xlsx Attached is a new draft version. The major changes are that I've included a column for the estimated noise levels at VLF frequencies for "Quiet Ship" (2 knots). The second VLF column is for estimated noise levels at VLF at the onset of cavitation. I will probably add a column for the estimated cavitation speed at PD. I'm also trying to refine the screw design column a bit. Let me know if you have any comments.

[CV60LCC19]

Interesting document, laying out the possible noise reductions in db and frequencies of various sound silencing technologies. Only for ships, but I assume that the numbers are reasonably accurate for submarines. May be useful for guestimating radiated noise levels Ship Underwater Radiated Noise.pdf .

[CV60LCC19]

Here's the current version of my submarine sheet. A couple of notes: I've added a column for the estimated cavitation speed at Periscope Depth, based on the prop design. The first column pink VLF column is for sound levels at 2 knots/quiet speed. The second VLF column is for estimated noise levels at the onset of cavitation. My various sources are attached in the second tab. Doing it this way is useful in it allows me to correlate the various references, most of which appear to be for targets moving at "operational speeds" (approximately 7 knots). It also allows me to break out ships with particular design issues. For instance, the project 877 Kilo SSK had an unusually small propeller, which, because it turned more quickly, created cavitation earlier. Hence, despite being an otherwise stealthy design at slow speeds, at operational speeds it was noisy.
One other point: the year of the submarine is important. Many of these subs received quieting modifications during their operational life (Cf., the HMAS COLLINS class). My estimates are based on the year provided.

Sound Levels of Submarines-4 DRAFT.xlsx

Comments on the presentation, methodology, etc would be greatly appreciated.

[CV60LCC19]

Is this spreadsheet something you want me to continue to work on? I haven't heard anything for awhile, so I'm not sure if I need to continue to work on it. Let me know

[smcclaire]

Hi CV60LCC19 -- in terms of the research I have been doing there is plenty of data already. I will defer to PygmalionOfCyprus in terms of DB needs. Thanks again for all your help!

[PygmalionOfCyprus]

I think we have plenty of info for an initial implementation. (Which, I know I said would come soonTM. Sorry. Lot of big pro stuff recently.) Once I actually fix/implement the sound level override and we add this stuff, you can critique our initial pass and then continue down the line if you have more platforms you'd like us to bring to standard.

[claudejdev]

Have you guys seen this? https://www.admiraltytrilogy.com/pdf/Historicon_2023_PLAN_Nuclear_Submarine.pdf https://www.andrewerickson.com/2023/08/china-maritime-report-30-a-brief-technical-history-of-plan-nuclear-submarines/

[CV60LCC19]

I haven't seen the updated slide. Thanks for sharing!

[PygmalionOfCyprus]

@Jkryos, see above for sub sigs rework.

[claudejdev]

Wildly relayed by the (French) press at the time, admiral Prazuck mentioned that the Suffre class will be "10 times quieter" than the Rubis class. [with its Amethyste update or the base, louder, class?] "Quieter than a shrimp school", mentioned a Naval Group "director".

https://www.meretmarine.com/fr/defense/suffren-gros-plan-sur-le-nouveau-sna-francais https://www.ouest-france.fr/economie/lancement-du-suffren-nouveau-sous-marin-nucleaire-discret-et-polyvalent-6441310