Sphere Sonar Frequency Range Sensitivity

[LuftWolf]

Ok, there has been a call for increasing the sensitivity of the sphere arrays and I intend the next version of the LWAMI Mod to have precisely this.

However, there are two ways to do this.

I can decrease the minimum frequency that they detect or I can decrease the ambient noise at the sensor surface (meaning a greater signal gain).

My preference on how to do this is based on the real-life parameters of the sensors, however there is no publically available data (on Google anyway) about this.

Does anyone know if the sphere sensors really only can detect high freqency and broadband signals? Or can the sphere sensors detect low frequence NB signals as well?

Please don't get yourself in trouble with the DOD in answering this question.

[SeaQueen]

Originally Posted by LuftWolf

However, there are two ways to do this.

I can decrease the minimum frequency that they detect or I can decrease the ambient noise at the sensor surface (meaning a greater signal gain).

...

Does anyone know if the sphere sensors really only can detect high freqency and broadband signals? Or can the sphere sensors detect low frequence NB signals as well?

Please don't get yourself in trouble with the DOD in answering this question.

Without actually looking at any data or thinking too hard about this, my physical intuition is that the arrays shouldn't be very good at detecting signals with wavelengths larger than the array itself. So... dropping the minimum frequency strikes me as a bad idea.

Since the whole point of putting a sonar array on the bow of the boat is to lower the self noise of the array, the smartest number to experiment with is probably that one.

Oh, and technically speaking, all arrays can detect both narrow band a broadband signals. This is a signal processing issue, not an array issue. I'm unsure of why they didn't model both narrowband and broadband displays for all of them.

I've never been aboard a submarine, though.

[LuftWolf]

Ah, SeaQueen, thank you!

I posted that question specifically hoping that you would answer.

Without actually looking at any data or thinking too hard about this, my physical intuition is that the arrays shouldn't be very good at detecting signals with wavelengths larger than the array itself. So... dropping the minimum frequency strikes me as a bad idea.

That was my feeling as well, I don't think the sphere arrays on submarines are THAT large, compaired to what can be achieved in the size of the flank or towed arrays. However, the ambient noise should be considerably less on that sensor given the ownship shielding and flow-noise reducing nose cone design.

Thank you thank you!

You're the best!

Cheers,
David

[Bellman]

SQ. :|\ Youre solid gold.

I've never been aboard a submarine, though.

You will be very welcome aboard my 'Yellow Submarine' anytime - I need a secret weapon.

LW - We need to send a Press* Gang to Washington

* French preter, ' to lend'

[SeaQueen]

Originally Posted by LuftWolf

That was my feeling as well, I don't think the sphere arrays on submarines are THAT large, compaired to what can be achieved in the size of the flank or towed arrays. However, the ambient noise should be considerably less on that sensor given the ownship shielding and flow-noise reducing nose cone design.

You're welcome. I'm probably exactly wrong, but you're welcome. :-)
What is the lowest frequency in the database for the sphere on a LA class submarine anyhow? I have my guess and I'm curious what's in there.

[LuftWolf]

800hz...

[SeaQueen]

Originally Posted by LuftWolf

800hz...

That's a perfectly reasonable estimate. My estimate was a little lower, just figuring out when complete destructive interference would occur between the signals from two hydrophones, but what they have is fine. It really depends on what one guesses to be the furthest apart two hydrophones could be spaced and still receive the same plane wave impinging upon them.

You'd probably be surprised how accurate sitting down and figuring out the dumbest possible answers one could arrive at are, just by trying to understand the physics that's involved.

Believe it or not, that's a lot of what intelligence services do. They just take publically available data and see how far they can extend it.

[LuftWolf]

You've made my day from 2000 miles away.

[SeaQueen]

Originally Posted by Bellman

SQ. :|\ Youre solid gold.

You will be very welcome aboard my 'Yellow Submarine' anytime - I need a secret weapon.

LW - We need to send a Press* Gang to Washington

* French preter, ' to lend'

You'd be amazed at how useless a scientist on a warship can be. We get referred to derogatorily as "riders" by the sailors, although I have to say, so far every sonar technician I've met was really cool. They're one of the more intelligent rates, though. Those guys are a little different from the poor little kids who basically got offered prison time or the Navy by some judge, and spend all day chipping rust off the deck.

[LuftWolf]

I couldn't imagine going to MIT or Cal Tech and then winding up as an enlisted Navyman, but I've heard the Navy technical programs (AEGIS, nuclear, WEPS, etc) are *extremely* competitive, primarily because it is job security for life once you get out with an Honorable Discharge and your sea time.

[SeaQueen]

Originally Posted by LuftWolf

I couldn't imagine going to MIT or Cal Tech and then winding up as an enlisted Navyman, but I've heard the Navy technical programs (AEGIS, nuclear, WEPS, etc) are *extremely* competitive, primarily because it is job security for life once you get out with an Honorable Discharge and your sea time.

It's not uncommon. An awful lot of enlisted people in the military have college degrees, some of them are from quite prestigious universities. Yesterday I was hearing about some work done by an enlisted SEAL with a math degree. It's a symptom of having an educated population.

From what I've seen, though, the people who seem to get the most out of the military are the people who would do well anywhere, just because they have access to a lot more programs than other people. If you have barely a highschool education, then you're much more likely to be a rust chipper than a missile shooter or a sonar technician, especially early on and most of these kids would have to be crazy to stay in for 10 years as rust-chippers just to not be a rust-chipper. It's just like the rest of the world, education opens doors.

And yeah, people with hands-on experience in some of the more challenging jobs in the military (not just rust chippers) can get some really nice jobs. There's defense contractors like Raytheon, Northrup Grumman, and Lockheed-Martins that really like to hire ex-militaries with engineering backgrounds. There's also a lot of think-tanks, like CNA, SPA, CACI, Mitre, and what not.

There's a lot of money to be made in the war business. For certain people, becoming a civilian contractor is very much just a continuation of their military career (without a lot of the nonsense).

[Amizaur]

OK, so I guess we should go rather for increased sensivity, than lower minimum frequency :-)
And a torpedo passive seeker lower frequency limit should be....? Currently it's a zero :-) same for UUV, so UUV sometimes detects easily in LF contacts not heard on Spherical/cylindrical...

[SeaQueen]

Originally Posted by Amizaur

OK, so I guess we should go rather for increased sensivity, than lower minimum frequency :-)
And a torpedo passive seeker lower frequency limit should be....? Currently it's a zero :-) same for UUV, so UUV sometimes detects easily in LF contacts not heard on Spherical/cylindrical...

Good question. I don't know. I suspect it'd probably be on the order of the torpedoes active sonar frequency. If that was the case, then this might solve a lot of the issues with the torpedos homing on things a long way away too, because high frequency sound should be attenuated much more strongly in water than low frequency sound. So if you upped the minimum frequency to the kHz range, then it'd only be able to home on sounds that are, by their nature only able to travel so far.

It'd also make EVERYONES torpedoes a lot less effective, much to the chagrin of all sides.