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By: - 3rd February 2010 at 18:18 Permalink - Edited 1st January 1970 at 01:00
How could you discern the QM2 from the ambient noise at that range? Sounds farcical.
By: - 3rd February 2010 at 19:20 Permalink - Edited 1st January 1970 at 01:00
Astute couldn't pick up twojags farting in the bath 3000miles away, let alone QM2
By: - 3rd February 2010 at 21:06 Permalink - Edited 1st January 1970 at 01:00
On page 2 of the attached report there is a graph that shows the reduction in Noise Levels of US Nuclear Submarines from 1955 through 2000. They are currently in the same realm of 110 dB. The ordinate scale states that (dB re 1 micro Pascal at 1 yd)
http://www.northropgrumman.com/analysis-center/paper/assets/analogues_stealth.pdf
By: - 4th February 2010 at 00:59 Permalink - Edited 1st January 1970 at 01:00
On page 2 of the attached report there is a graph that shows the reduction in Noise Levels of US Nuclear Submarines from 1955 through 2000. They are currently in the same realm of 110 dB. The ordinate scale states that (dB re 1 micro Pascal at 1 yd)http://www.northropgrumman.com/analysis-center/paper/assets/analogues_stealth.pdf
Like this bit
Figure 1. This estimate of total radiated sound levels for US nuclear submarines suggests a noise reduction of 60 dB [from 170 to 110] over
45 years. Modern submarines emit about one-millionth of acoustic energy as did their predecessors.
By: - 4th February 2010 at 13:59 Permalink - Edited 1st January 1970 at 01:00
When looking at the paper it appears that SSBN's are a lot quiter than SSN's. Is there a reason for this? I still dont get the db noise and how this translates to actual noise you can hear on land.
By: - 4th February 2010 at 15:01 Permalink - Edited 1st January 1970 at 01:00
When looking at the paper it appears that SSBN's are a lot quiter than SSN's. Is there a reason for this? I still dont get the db noise and how this translates to actual noise you can hear on land.
SSN are smaller and cheapper. In SSBN you don't do any compromise with the noise. But the price is hight, in term of performance (speed) and... in term of price.
@+, Areka
By: - 4th February 2010 at 15:23 Permalink - Edited 1st January 1970 at 01:00
Here is the story about HMS Astute being able to detect the QE2 leaving new york harbour. It doesn't say that it has done this only that it is possible.
The Astute, the first attack submarine to be built in Britain almost two decades, has a listening system that can detect the QE2 cruise liner leaving New York harbour from the Channel.
This item is also mentioned in a BAE press release.
With a radar signature equivalent to a dolphin, it can remain undetected thousands of miles from home and hundreds of metres underwater. In the right conditions it can detect the QE2 leaving New York harbour from the English Channel.
Now it says that HMS Astute has the same radar signature as a dolphin. I'm not sure this is relevant as don't you detect nuclear submarines using sonar and listening devices? It must be one impressive dolphin if it can pump out 110db of noise. I would think if the submarine is to be compared to anything it would be a blue whale.
Some of the stories say that it won't need it's reactor refuelled in its 25 year service life and some say it's 35 year service life. Anyone know which is accurate? I'm guessing that if it's 25 years and you run it for 30 years without refuelling the reactor would just provide a little less power as it went past 25 years? I'm no nuclear expert so i'm guessing here.
By: - 4th February 2010 at 15:37 Permalink - Edited 1st January 1970 at 01:00
Here is the story about HMS Astute being able to detect the QE2 leaving new york harbour. It doesn't say that it has done this only that it is possible.
The Astute, the first attack submarine to be built in Britain almost two decades, has a listening system that can detect the QE2 cruise liner leaving New York harbour from the Channel.This item is also mentioned in a BAE press release.
With a radar signature equivalent to a dolphin, it can remain undetected thousands of miles from home and hundreds of metres underwater. In the right conditions it can detect the QE2 leaving New York harbour from the English Channel.
Now it says that HMS Astute has the same radar signature as a dolphin. I'm not sure this is relevant as don't you detect nuclear submarines using sonar and listening devices? It must be one impressive dolphin if it can pump out 110db of noise. I would think if the submarine is to be compared to anything it would be a blue whale.
Some of the stories say that it won't need it's reactor refuelled in its 25 year service life and some say it's 35 year service life. Anyone know which is accurate? I'm guessing that if it's 25 years and you run it for 30 years without refuelling the reactor would just provide a little less power as it went past 25 years? I'm no nuclear expert so i'm guessing here.
I'm pretty sure its 25 years service life for the reactor.
Re: the noisey Dolphin, I'm pretty sure from memory it was something to the effect of "Makes as much noise as a baby Dolphin".
By: - 4th February 2010 at 22:09 Permalink - Edited 1st January 1970 at 01:00
A Bel and hence a Decibel is a ratio of signal loss.
i.e. the more decibels the quieter
So a 110 dB submarine is quieter than a 100 dB chainsaw
Its also a logarithmic ratio (base 10) so a 10 dB difference is a significant difference
By: - 5th February 2010 at 01:59 Permalink - Edited 1st January 1970 at 01:00
Jet engine at 30 m = 150 dB
Threshold of pain = 130 dB
Hearing damage (possible) = approx. 120 dB
Jet at 100 m = 110 – 140 dB
Traffic on a busy roadway at 10 m = 80 – 90 dB
TV (set at home level) at 1 m = approx. 60 dB
Normal conversation at 1 m = 40 – 60 dB
Very calm room = 20 – 30 dB
calm breathing = 10 dB
Auditory threshold = 0 dB
Less decibel is not louder.
By: - 5th February 2010 at 05:52 Permalink - Edited 1st January 1970 at 01:00
How could you discern the QM2 from the ambient noise at that range? Sounds farcical.
I may be showing my age - and technology will obviously have improved things - but my understanding is this: propellor-screws are individually manufactured, resulting in unique imperfections and characteristics. As such, each ship emits unique cavitation signatures.
Assuming that this still holds true, it should be possible to detect a ship by the noise it generates. I may have misread, but only gf0012-aust can confirm/deny otherwise. :cool:
By: - 7th February 2010 at 12:49 Permalink - Edited 1st January 1970 at 01:00
The comment on the Astute is more to do with the processing capability of the sonar rather than its sensitivity.
Very simplistically in any body of water, of sufficient depth, there are different layers deliniated by water temperature as anyone who's read a Tom Clancy novel is likely well aware. In oceanic waters there is a condition known as the deep sound channel. This can carry acoustic signals over oceanic distances - whales use this to communicate with each other over vast distance - so, if you trail a sensitive array in the channel and have the processing power to isolate discrete signals amongst the background you can make a detection.
Getting a good value for range on that kind of contact is very hard. Triangulation is a swine when you have one leg thats 3000nm long!. You really do have to motor to get a worthwhile baseline!. So you aren't tracking anything, but, it makes a great soundbyte saying that the sub can detect the QE2 on the other side of the Atlantic!.
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By: F35b - 3rd February 2010 at 17:20
I was reading about the Type 93 Nuclear attack Submarine that is made by China. While reading it says it has an estimated noise level of 110db. The first thing i thought was how is this measured? IS this the noise inside the engine room or outside the hull from a set distance?
Next thing i thought was that is really loud. i'm sure a chain saw is less than 100db. There was a guy on the TV the other day ( i think he's an opera singer) trying to break the record for the loudest human noise, He managed 108db and he was loud. i can hear an aircraft or helicopter in the sky when they are miles away but they may be louder than 110db.
Does anyone know how this compares to other submarines? My thoughts were this is loud and i thought some sound travelled through water much further than in air.
Then i remember reading that the HMS astute picked up the QM2 leaving new york. I found this a bit hard to believe that with all the ships in the Atlantic a submarine's sonar could identify a ocean liner over 3000 miles away. Maybe what it meant was that the sonar on HMS Astute has the ability to pick up a cruise ship on the other side of the ocean. Anyone else heard this story?