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Killing whales for empire
Marine mammals won a significant victory today in the US District Court, Northern California. Magistrate Elizabeth Laporte ruled that the US Navy, which has been trying to increase its use of high-tech active sonar in the open oceans, must establish sonar-free zones in sensitive ocean habitats around the world. The Bahamas, the Great Barrier Reef, the Galapagos Islands, Davison Seamount off Monterey Bay, and several other spots around the world were mentioned.
A week ago, a related decision was handed down by a federal judge in Los Angeles, who refused to exempt the Navy’s active sonar tests from environmental laws.
The issue is profound and usually mortal injuries that whales and dolphins, and likely other types of marine life, suffer, directly or indirectly, from exposure to intense bursts of artificial sound such as active sonar pings. Mass strandings of cetaceans have been documented after sonar tests in the Bahamas, the Mediterranean, and elsewhere. On her blog Cocktail Party Physics, Jennifer Ouellette has posted one of the best summaries of the issue I’ve seen, discussing the political and scientific angles.
The sonar tests at issue involve mid-frequency sounds, from about 1 to 10 kHz, a bit more than a three octave range, with the low end pitched about here:
and the high end here:
A few years back the Navy was going through similar court battles regarding Low-Frequency Active Sonar, which uses sounds of about 250-300 hertz, about like this:
Keep in mind that those sound samples are almost unbelievably quiet compared to the sonar pulses we’re talking about. How loud they are when you play them depends on your machine and its settings, but let’s assume you have it turned up to about as loud as a typical conversation in a quiet room. That’s about 60 decibels or so. Decibels (dB) are defined logarithmically, remember: an increase of ten dB means a tenfold increase in volume, so that 70dB is ten times louder than 60, 80dB is 100 times louder than 60, and so forth. A noise of 160dB, a billion times louder than 60dB, will destroy your eardrums instantly.
The midlevel active sonar pings being discussed range around 230dB. Water conducts sound much more readily than does air, and 300 nautical miles away from the test zone, the ping may only have attenuated to about 140dB, about like standing next to a military jet taking off. That’s also the level the Navy has set, after study, as the loudest underwater sound to which one of its divers can be safely exposed. Cetaceans, with senses of hearing unimaginably more sensitive than humans’ — humpbacks have been observed carrying on conversations across distances of hundreds of miles — get a whole lot louder sounds than that “safe level” if they venture within 300 miles of a test.
So why is the Navy carrying on these tests at all? As Jennifer Ouellette puts it:
From the Navy’s perspective, sonar training exercises are critical to US national security interests: smaller diesel submarines can’t be detected with passive sonar, for example, and over 40 nations deploy these kinds of subs. Ultimately, it’s about balancing the interests of national security with environmental concerns. That makes it one of those complex issues about which reasonable people might reasonably disagree.
Now it had to happen eventually, and frankly, I’m as surprised as you are. But Jennifer is, in those last two sentences, well, wrong.
Diesel-electric submarines are indeed quiet — when they operate on electric power only. But submarines are heavy, and water dense, and moving the sub through the water takes a lot of power, and batteries don’t store all that much, and batteries are heavy too, so adding more of them reaches a point of diminishing returns. Thus the range of a diesel-electric sub under electric power only is rather limited. Eventually, the crew has to start up the diesel engines to recharge the batteries. Diesel engines are noisy, and thus detectable by passive sonar, a fancy phrase the Navy uses to describe the act of just listening for ships. And despite the rise in ocean noise over the last decades, the Navy does that just fine. In February 1997 Rear Admiral Edmund Giambasriani, the US Navy’s Director of Submarine Warfare, told Jane’s Defense Weekly,
Our view is that because of significant capabilities in processing, sensor apertures and the ability to net sensors together, passive [sonar] is not dead ... We feel there is [sic] still a lot of dB out there that we can mine.
“Capabilities in processing” have only increased since then. When Giambasriani said the above, the Cray T90 was the mythical supercomputer of record. They weighed fourteen tons and the US Government owned maybe three of them. I have a somewhat more powerful computer sitting next to me here playing Sam Cooke as it works. Sorting out diesel-electric sub noise from tanker and outboard noise becomes a routine task for Navy software engineers.
What’s more, diesel engines rely on burning their diesel fuel, which requires oxygen, which is in limited supply in a submerged hull and necessary to keep the crew alive besides. So in order to run the diesel engines, the crew has to surface. This exposes the sub not only to detection by way of passive sonar, but also by means of sophisticated sensing technologies such as these.
What this all means is that those 40 nations that deploy diesel-electric submarines in their naval fleets use them in littoral settings, close to the coast. This further means the subs are used in defensive settings. There they are effective: they can keep their batteries charged until someone invades and then hide, waiting for the right moment to sink the aggressor’s boats.
Were the US faced with the prospect of defending its shores, in fact, diesel-electric submarines would be far more useful than fancy whale-killing sonar. But the fact is, there are no diesel-electric submarines in the US Navy’s fleet. If they’re a new and terrifyingly effective way of defending coasts, why does the US Navy own none of them?
Because defending the US is not at issue here, that’s why.
With occasional odd exceptions, and unless US-Canadian relations continue to degrade, the US Navy will only encounter hostile diesel-electric submarines in the course of invading other countries. That is the only field of battle in which active sonar of any kind becomes necessary.
The active sonar issue is not, and never has been, a matter of balancing environmental protection and national defense. It’s a matter of defending the natural world, again, against the depredations of a US policy that is at best interventionist, at worst imperialist. We should be working to stop active sonar tests even if no marine life is harmed by them.
Posted by: Chris Clarke
Note: A database glitch in 2008 ate a bunch of archived comments. Don't be offended if yours isn't here, or confused if the conversation seems disjointed. Thanks!
Thanks for putting this into layman’s terms, Chris. I had a strong feeling that this was how things lay, but I couldn’t back it up.
By: By Dave on 2008 02 07
So, we have spy satellites that can tell what I am wearing when I get into bed but cannot tell the difference between a whale and a submarine under water. Only sonar can do that for the US Navy. Imagine that.
The cynic in me wonders what government contractor owns the sonar business here.
By: By Allegra on 2008 02 08
I hate to break it to Chris but I am frequently wrong. :) On this issue, though, I do think there’s room for reasonable disagreement. Personally, I’m all for a ban on active sonar testing; I don’t buy the “national security” argument either. But everyone I’ve spoken to (dozens of folks)—scientists, the lawyers for the environmental groups, other environmental reps—described it as an issue of balancing national security against environmental protections. And most of those _don’t_ advocate an outright ban on sonar testing.
It’s a new issue for me, and I’m sure chris has followed it more closely over the years, and is far more knowledgeable. But so are the others I spoke with, all of whom I consider to be reasonable folks. And yet they disagree. So I stand by my original statement. :)
By: By Jennifer Ouellette on 2008 02 08
I hate to break it to Chris but I am frequently wrong.
I’m not sure that’s accurate.
By: By Chris Clarke on 2008 02 08
Chris, I think it’s worth pointing out that you have to be careful about using decibels SPL when you’re talking about sound pressure or intensity in water.
In air, dB SPL are referenced to an RMS sound pressure of 20 uPa, which corresponds to a sound intensity of 1 x 10^-12 W/m^2. In water, the 0 dB reference is 1 uPa RMS, which, due to the fact that the characteristic impedance of water is approximately 3600 times that of air, corresponds to a sound intensity of approximately 6.67 x 10^-19 W/m^2.
You cannot compare sound levels in the two media directly by using decibel notation without adjusting for the different reference levels and acoustic impedances.
Also, your statement that seawater conducts sound better than air fails to take into account that a spherically diverging wave will always follow an inverse square law as far as intensity (power/area) is concerned and an inverse linear law for sound pressure.
At distances comparable to or greater than the depth of the water, the limited depth of the medium may result in a cylindrically diverging wave, in which case the intensity would follow an inverse linear law and the sound pressure would drop off as the inverse of the square root of distance.
Without knowing the distance at which the intensity of the source is measured and how the wave propagates it’s impossible to calculate the intensity at a given distance.
Empirical evidence of the effects of sonar on marine wildlife is more than good enough. There’s no need to throw around numbers in a way which very few readers will be able to comprehend, and which I fear you yourself don’t really comprehend.
By: By Ktesibios on 2008 02 09
Yes. The impedance of water is greater than that of air, and thus the sound pressure in water would be lower for equivalent sounds. A more thorough article would have mentioned this.
I made what was probably a bad choice not to mention it in part out of concern that readers eyes would glaze over, in part due to the fact that the mechanism by which high-intensity sounds hurt marine mammals is unknown and thus sound pressure (as opposed to intensity) may well be irrelevant — reflexive responses to loud noises may be at issue, rather than direct physical damage caused by the sound waves — and in part because the relevant numbers I did use were obtained from US Navy documents and thus presumably wildly optimistic as regards the potential dangers.
The Navy refuses to subject its divers to underwater sounds of more than 140dB, for health reasons. They subject marine mammals to significantly more than that, over potentially hundreds of square nautical miles of ocean. Does it matter how far away the source is, and how loud the sound at the point of origin? I’m thinking no.
But you’re right. I should have mentioned the difference in impedance between the two media. That’s a flaw in the post.
As for your final line, all I can say is that you may be unfamiliar with this site. We relate to one another here as adults and try to converse in good faith. You’re welcome here if you can live up to that standard.
By: By Chris Clarke on 2008 02 09
Actually it should be understood that what navy lady there is talking about is the Kilo class diesel submarine, and even more specifically she’s really talking about Iran and China’s Kilo class submarines that they bought off the russians at some point.
Which actually are really quite super-duper quiet, though that’s because they’re really really well designed more than because they’re diesel powered (which can in fact operate their diesel engines underwater actually (and have done so since the latter half of ww2 when germany invented the method used) using a sort of advanced stealth snorkel - a nuclear generator would make them better of course (and also more expensive), but the Kilo class was an export design russia could sell without violating any proliferation treaties).
In fact the Kilo is so well designed that even active sonar doesn’t work too well against them - because they’re covered in a special material which means that sonar doesn’t bounce off them as it normally would while also make them a bit harder to track with passive sensors.
Which means that A) the best way to catch Kilo subs is to focus on detecting their snorkels on the surface (which the navy doesn’t like because it takes the job away from the H/K and Destroyer/Cruiser crews and gives it to the navy air crews who are just better at anti-submarine warfare anyway) and B) training with active sensors doesn’t actually help all that much - they’re not appreaciable more detectable with active than with passive sensors.
But a company sold the newest active sonar systems to the US navy and the navy brass has in turn been <strike>paid huge amounts of money</strike> convinced with sound logic to make the Navy find a reason to keep buying the things despite a rather shocking lack of need inherent to a modern post-soviet world - so here we are, killing dolphins so that we can… not go to war with China because they have nukes.
So Go ‘nar! Woo!
Also: bitching about the thing with the impedance of sea water is even sillier considering most of Chris’ facts about diesel submarines are about 70 years out of date (so if anyone really feels the need to nitpick…) - and even then his arguement isn’t harmed too badly by that because “can’t be detected with passive” is an outright lie by any measure - ultra modern diesel subs like the kilo class are difficult to find with passive sensors, but far far from impossible - and difficulty in spotting is less an issue of being seen at all, and more about the range at which they can be reliably detected. And I’m not too sure about the “40 countries” bit either, I’d actually reckon that about 30 of those countries have crappy 1960’s era diesel subs which are about as stealthy as a brick with a large outboard motor on the back end. And most of the rest are probably in northern europe, if one isn’t actually switzerland. So unless it’s felt that finland may suddenly send wave after wave of their royal kamikaze submarine coast guard at america…
I was sleeping with a slightly chubby military historian who specialized in modern naval history once, and later that very night I had one of those dreams where you’re eating a giant marshmellow… And when I woke up the next morning I found the historian was gone!
Ever since my knowledge of randomized military crap has been rather alarmingly huge.
I regret nothing.
By: By R. Mildred on 2008 02 10
Well, eight years out of date, maybe. Haven’t worked much on Active Sonar since 2000 or so. But at that point, I was as current as Jane’s allowed me to be, if superficially.
By: By Chris Clarke on 2008 02 10
Nope, not good enough, honor demands that for trying to get away with simplifying stuff about water impedence we’re gonna have to throw you into an active volcano.
Not knowing about submarine snorkels may mean that we’ll also have to introduce you to madame Gillettene™ afterwards.
By: By R. Mildred on 2008 02 11
we’re gonna have to throw you into an active volcano.
I’m not worried. That sentence will certainly be tossed out when my case gets to a-Pele-t court.
By: By Chris Clarke on 2008 02 11
