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How poeple and animals use sound in the sea
October 3, 2006 10:35 PM   Subscribe

How poeple and animals use sound in the sea
posted by persona non grata (12 comments total)

 
*cough*
posted by weapons-grade pandemonium at 10:42 PM on October 3, 2006


Ok, I loved Ragdoll Avalanche.

This, not so much.
posted by knave at 10:45 PM on October 3, 2006


poeple is an anagram.
posted by persona non grata at 10:52 PM on October 3, 2006


hmm... here's a slightly more provocative link about sonar devices used by the US navy that produce sound over 230 decibels "as loud as a Saturn V rocket blasting off" (apparently). this pretty much melts whale brains.
posted by wumpus at 11:16 PM on October 3, 2006


They think they're peoples!
posted by Astro Zombie at 12:18 AM on October 4, 2006


Soylent Green is poeple! It's poeple!
posted by mrnutty at 12:32 AM on October 4, 2006


sigh.... *debates whether or not to even get started*.....

Not to be the heavy here, but wumpus is not kidding about the "melts whales brains" thing. The sound can be so loud whales try to escape the water. The sound can be so loud whales' ears start bleeding. Especially since there are quieter options, I can't believe I live in a country where it takes an ongoing series of legal battles to try to force the Navy to stop doing this.

"In March 2000, the [US] Navy was using a high-intensity, mid-frequency sonar in the Bahamas.... the first whale to strand landed on the beachfront property of a marine mammal scientist. He preserved some of the whales' heads in the refrigerators of nearby restaurants and they were then shipped to New England for tests. [CAT scans] were done and bleeding was found around the whales' brains and in their ears. In December 2001, the Navy and the [US National Marine Fisheries Service] issued a preliminary report... stating that the most likely cause of death was acoustic trauma."
-- Marsha Green, Ph.D., founder Ocean Mammal Institute, "Fighting Intense Underwater Noise Pollution," Warrior Mothers

More facts from that article: whales start trying to escape sounds that are 120 dB. Physical harm to marine mammals starts to occur around 150-160 dB. (Decibels are logarithmic, so 130 dB is 10 times as loud as 120 dB, 140 dB is a hundred times as loud, etc.) When you read about sonar that's around 230 dB, that's literally ten million times louder than something known to cause injury.

posted by salvia at 1:12 AM on October 4, 2006


Not just sonar, Seismic air guns used in oil exploration are powerful enough to cause physical damage, at close range they can break bones. In the UK the JNCC have issued Guidelines for minimising acoustic disturbance to marine mammals from seismic surveys.

The extent to which seismic disturbance from airguns affects cetaceans is not well known for all species due to the limited research carried out to date.
posted by Lanark at 1:21 AM on October 4, 2006


230 decibels "as loud as a Saturn V rocket blasting off"

That's insane. Seriously, I find myself unable to comprehend a sound that loud. According to this, 115db is dangerous after 30 seconds. If memory serves 140db can cause nearly instant permanent hearing damage.

And because decibels follow an logarithmic curve each db is nearly twice as loud as the one the preceded it. (kinda)

As such 230db is a quantity I'm having a hard time getting my head around. Melting brains indeed.
posted by quin at 1:28 PM on October 4, 2006


If 230dB is possible, it'd be a shock wave, wouldn't it?
posted by pax digita at 2:49 AM on October 5, 2006


The term "shock wave" refers to a wave caused by an object moving faster than the speed of waves in the particular medium. In air, jets traveling at or above Mach 1 create shock waves, which are pressure waves that build up from the inability of the waves to propagate away from the source -- the source is moving two fast. This is heard by bystanders as a sonic boom.

In the case of the 230dB sound, it's just a really loud sound. I don't think there's a special class for it.

And yes, 230dB must be incredible. I was in pain after firing 5 rounds from a .45 handgun, without wearing ear protection. I had to stop and borrow some ear plugs to continue, and I won't shoot again without them! (The site linked above classified gunfire as 140dB to 190dB, so 230dB would certainly be ear-bleeding-loud!)
posted by knave at 4:39 AM on October 5, 2006


I've fired a lot of .308, 7.65, 8mm etc. w/ "proper" ear protection and have measurable h/f hearing loss in the ear that the side of the rifle was on at an earlier age than the average. I'm hoping you don't have similar problems.

My understanding of undersea acoustics comes chiefly from background reading I've done to understand Tom Clancy novels and the Sonalysts/EA Seawolf submarine warfare simulation (be careful around whom you call it a "game"!). I'm used to thinking in terms of really low dB for acoustical energy, and like others, I'm having a terrible time imagining what 200+ dB would do. If it's not a "shock wave," as I mischaracterized it, do I think of it as increased, sustained sound pressure? Overpressure can be a veddy bad things in submarines, especially if you localize it -- which is what a detonating torpedo does. So this is a bit like a detonating torpedo, only all over the sub's hull, continuously?
posted by pax digita at 12:37 PM on October 5, 2006


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