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Old 28th August 2003, 06:06 PM   #1
massive is offline massive  Netherlands
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Angry 215 decibel !! Could be dangerous

In the news:

Scientists have discovered that bursts of intensive sound can tear the delicate air-filled tissues around mammals' brains and ears, resulting in hemorrhaging and death.

The shipboard system consists of an array of 18 speakers capable of releasing 215-decibel bursts of low-frequency waves that can travel hundreds of miles before dissipating. The Navy says Russia and other nations have new, highly elusive submarines, and stresses that it needs the sonar to detect them in a timely manner to protect warships.

The judge also emphasized the need to warn human divers about the sonar -- as the Navy has done in Guam -- to reduce the potential for casualties from panicked divers.

The opinion cited a study that one diver experienced "lightheadedness, dizziness, difficulty hearing, vibration in his arms, hands and distal lower extremities and shaking" at 160 decibels, prompting the Navy to reduce exposure in subsequent tests with human subjects.

Public concern has been heightened by incidents where exposure to another kind of Navy sonar has led to lethal strandings of whales on the beach, as in the Bahamas in 2000.


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Old 28th August 2003, 06:38 PM   #2
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Holy Crap!

215? I sure hope that's a typo... The 18 speakers must be Tumults...
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Old 28th August 2003, 07:22 PM   #3
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Correct me I'm wrong:

120 dB = 1W/sqr meter => 215 dB is 95 dB more than 120 = 10EXP9.5 (9.5 powered to 10) = 3.162 GW!!!!

It must be true!
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Old 28th August 2003, 07:29 PM   #4
indoubt is offline indoubt  Netherlands
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I predict more powerfailures, better get an emergency powersupply
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Old 28th August 2003, 07:44 PM   #5
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If it's shipboard sonar it's going to be puled. (Consider RADAR often has ratings up to similar levels (gigawatts), but for nanoseconds.) Damned if they ever could go continuous though!

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Old 28th August 2003, 08:25 PM   #6
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Quote:
3.162 GW!!!!
Pulsed or continuous I think it'll take a flux capacitor and a DeLorian w/ a pair of A-7 horns to come up with that much power.
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Old 28th August 2003, 09:19 PM   #7
moamps is offline moamps  Croatia
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Hi,

"Water" speakers have bigger efficiencies. You don't need gigawats to get huge power.IMHO
With the average atmospheric pressure of ca 1013 hPa, the maximum symmetrical SPL is about 188dB.

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Old 29th August 2003, 12:52 AM   #8
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Default Jigawatts!

Submarines have been using VLF (very LF) communications since the beginning of the various national SLBM programs. It doesn't take gigs of power or the reactors (or diesels) couldn't possibly supply it.

Of course, in most cases, the communications are one way as a sub that transmits anything gives away its position.

http://www.fas.org/nuke/guide/usa/c3i/vlf.htm

:)ensen.
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Old 29th August 2003, 02:53 AM   #9
mbroker is offline mbroker  United States
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I'm surprised they would use speakers. Non-lethal weapons development of directed high intensity sound usually uses pulsed explosions in a specially designed tube. I'm sure there's info on it on the Net. I've seen it on more than one Discovery Channel show.
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Old 29th August 2003, 03:28 PM   #10
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The system being described in Post#1 sounds more like the VLF array that is towed behind a vessel for long distance water borne communications. It is just an array of transducers and is not intended to be a weapon.

The transmission of waves through a medium that has damping characteristics will require a lot of energy. That, of course, can also cause injury.

It's a bit like the jigawatt guitar amp that Marty McFly tried to play in Back to the Future One. It's meant to be heard from a distance. Don't stand directly in front of it.

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