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Powerful Sonar Causes Deafness In Dolphins 323

Posted by Soulskill
from the sorry-flipper dept.
Hugh Pickens writes "Mass strandings of dolphins and whales could be caused because the animals are rendered temporarily deaf by military sonar, experiments have shown. Tests on a captive dolphin have demonstrated that hearing can be lost for up to 40 minutes on exposure to sonar and may explain several strandings of dolphins and whales in the past decade. Most strandings are still thought to be natural events, but the tests strengthen fears that exercises by naval vessels equipped with sonar are responsible for at least some of them. For example, in the Bahamas in March, 2000, 16 Cuvier's beaked whales and Blainville's beaked whales and a spotted dolphin beached during a US navy exercise in which sonar was used intensively for 16 hours (PDF). 'The big question is what causes them to strand,' says Dr. Aran Mooney, of the University of Hawaii. 'What we are looking at are animals whose primary sense is hearing, like ours is seeing. Their ears are the most sensitive organ they have.' In the experiment, scientists fitted a harmless suction cup to the dolphin's head, with a sensor attached that monitored the animal's brainwaves, and when the pings reached 203 decibels and were repeated, the neurological data showed the mammal had become deaf, for its brain no longer responded to sound. 'We definitely showed that there are physiological and some behavioral effects [from repeated, loud sonar], but to extrapolate that into the wild, we don't really know,' said Mooney."
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Powerful Sonar Causes Deafness In Dolphins

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  • 203 decibels? (Score:5, Insightful)

    by TheLink (130905) on Wednesday April 08, 2009 @12:31PM (#27505167) Journal
    Wow. I think if you expose me to a 203 decibel sonar, it's not just my ears that would go poof.
    • Re: (Score:3, Interesting)

      by daem0n1x (748565)

      Can sound get THAT loud? According to this [wikipedia.org], 115dB is the threshold of pain for humans. 203 dB is simply 33,000 times louder.

      If you account for the high sound sensitivity of dolphins and water being a better sound conductor, just imagine the damage! It's like dropping a bomb on your head.

      Couldn't the sonar be replaced by something less damaging? I guess water muffles radio waves, so a water radar is not a good idea. Maybe a very low frequency radar?

      • Re:203 decibels? (Score:5, Insightful)

        by Shakrai (717556) on Wednesday April 08, 2009 @01:28PM (#27505977) Journal

        Couldn't the sonar be replaced by something less damaging? I guess water muffles radio waves, so a water radar is not a good idea. Maybe a very low frequency radar?

        The problem with that theory is that you'd need such a low frequency that your wavelength would be hundreds to thousands of miles. The antenna requirements alone would make such a system impractical on a mobile basis. Some of the antennas used for ELF submarine communications systems were up to 20 miles long.

        Unless you can change the laws of physics I'm afraid we'll be stuck using sonar for the foreseeable feature. If you accept that then you have to accept the fact that the Navy needs to practice with it before they need it in an actual shooting war. Sucks that it apparently harms marine life but what can you do?

      • Re: (Score:3, Insightful)

        by geobeck (924637)

        Or passive sonar. Active sonar (pinging) is like standing in a dark field with a huge omnidirectional beacon. You'll probably see someone else standing around by the light reflected off them, but they'll certainly see you first.

        Passive sonar is like hiding in a dark corner of the field watching everyone else stumbling around with flashlights. Their lights may not be very bright (i.e., the ships' engines and hulls may be very quiet), but they always make some noise, which your super-sensitive passive sona

        • Re:203 decibels? (Score:5, Informative)

          by Macgruder (127971) <chandies.williamson@gm a i l .com> on Wednesday April 08, 2009 @03:17PM (#27507749)

          The thing of it is, submarines don't use, and don't need a super-powerful active sonar.

          This is for surface vessels ("targets" in bubblehead vernacular) searching for subs, not subs hunting each other.

          These hyper powerful sonar systems are for surface vessels to locate submarines that may be in the vicinity. When you get into costal areas, the noise of the surf, the temperature gradients (from the shallow bottoms) and the salinity gradients from the fresh water from the rivers, plays havoc with normal sound transmission.

          This massive system is used to plow through all that, and still return a signal clear enough to spotlight the sub lurking around the area.

          (former US Navy submarine Sonar Tech)

      • Re: (Score:3, Funny)

        >Couldn't the sonar be replaced by something less damaging? I guess water muffles radio waves, so a water radar is not a good idea. Maybe a very low frequency radar?

        I say we replace the submarines with dolphins. We can make them effective by attaching laser beams to them. This has the added bonus of allowing us to stop worrying about the dolphins until some genius decides to mount laser beams on sharks. But no one here would ever dream of doing such a thing, so we'll be good to go!

    • Re: (Score:3, Informative)

      At that sound level -and given the density of the transmission medium- it is most likely that the animal is experiencing actual physical damage to its brain if it is close enough to the transmitter. It was once postulated that Sperm Whales were capable of stunning their prey with a sonar 'blast' and it is known that the Pistol Shrimp, stuns its prey with a sonic 'click' [youtube.com]. This page [makeitlouder.com] has a listing of SPLs in db and the associated physical effects at that level in air.
  • by Em Emalb (452530) <(ememalb) (at) (gmail.com)> on Wednesday April 08, 2009 @12:33PM (#27505183) Homepage Journal

    Guess dolphins and whales can't go to concerts. Although, I hear The Pingers have quite the underwater following.

    In other news, when exposed to brilliant flashes of light, humans are rendered temporarily blind.

  • by fprintf (82740) on Wednesday April 08, 2009 @12:34PM (#27505209) Journal

    Experiments like these are like putting people next to a jet engine to see if their hearing gets damaged. I am no PETA freak, but putting 200+ decibels is bound to do permanent damage. I know they said it is temporary, but that might be like my "temporary" hearing loss from the Boston show a few months back. Yes, I could hear fine afterward* but I wonder what incremental loss I might have had from all that loudness.

    *I have higher pitch loss that apparently came from shooting a lot many years ago without hearing protection.

    • Re: (Score:2, Insightful)

      by esocid (946821)
      Your comparison isn't a good one. It would be like losing your vision for 40 minutes and wandering around with deep holes around for you to fall in. Once you're in those holes it's a fair chance you won't survive unless someone helps you out.
      Anything that is used for prolonged periods (16 hours) is going to have detrimental effects on the mammals' methods of navigation. Why is it such a terrible crime that the Navy consider what damage it does to its surroundings? Not implying you, it's just their stance is
      • by Shakrai (717556) on Wednesday April 08, 2009 @01:35PM (#27506083) Journal

        Why is it such a terrible crime that the Navy consider what damage it does to its surroundings?

        What makes you think they don't already or that the damage to those surroundings is more important than our ability to keep the sea lanes open in the next shooting war?

      • I'm going to have to declare Offtopic here, and due to my lack of mod points, I will just declare it publicly here.

        Your comparison isn't a good one. It would be like losing your vision for 40 minutes and wandering around with deep holes around for you to fall in. Once you're in those holes it's a fair chance you won't survive unless someone helps you out.

        OP was examining the long term effects of this experiment on the dolphins being experimented on and not the short term effects of SONAR use in the wild.

      • by CrimsonAvenger (580665) on Wednesday April 08, 2009 @01:52PM (#27506389)

        Why is it such a terrible crime that the Navy consider what damage it does to its surroundings?

        Because the design purpose of a Navy is to kill people and break things?

        Or are you really suggesting that they should spend more time finding ecologically friendly ways to sink ships and kill people?

        • by Orange Crush (934731) on Wednesday April 08, 2009 @04:45PM (#27509287)
          The goal of any military is to accomplish its missions with minimal collateral damage. At the very least, it's important to know the extent of damages that are being caused and if the cost is worth the benefit. Killing local marine wildlife every time they do a sub-hunting excercise might be cause to change their procedures a bit.
    • Re: (Score:2, Insightful)

      by Anonymous Coward

      I am no PETA freak, but putting 200+ decibels is bound to do permanent damage.

      Perhaps the experiment was inhumane. Hypocrisy demonstrated. Point taken.
      That does not change the conclusion: military exercises that include sonar cause injury to advanced marine life.

      The ramifications should be obvious, but just in case they aren't...

      Harming endangered species is illegal, and for good reason...their extinction could have unwanted ecological consequences and will certainly have unwanted sociological consequence

      • by Nutria (679911)

        nobody wants a PETA riot

        Sure I do! That way DHS swoops in, rounds them up, and (based on all the left-wing whining and ravings you see in places like /. and dailykos) throws them in Gitmo with thousands, nay, billions of other domestic political prisoners and Belgians.

      • ...could have unwanted ecological consequences...

        The building of Navy vessels most certainly has greater unintended/unwanted consequences than occasional deafening of advanced marine life. But either of those compared to a lack of preparedness on the part of our military to defend against threats foreign and domestic...Well, I guess it is all a matter of perspective.

    • by radtea (464814) on Wednesday April 08, 2009 @01:03PM (#27505597)

      I am no PETA freak, but putting 200+ decibels is bound to do permanent damage.

      The document linked on the Bahamas stranding says that source levels were 223 - 235 dB and levels were less than 180 dB at 300 m horizontally and 200 m vertically, so unless the dolphins were EXTREMELY close to the ships when the sonar was turned on the odds of even temporary deafness due to the use of sonar in the wild are quite low. Remember: a 40 dB difference in signal is a factor of 10,000 in amplitude of the pressure wave, so unless the dolphins were within a few meters of the source they would be very unlikely to get anything close to 200 dB.

      This is a bit like dropping a 10 kg mass on a person and noticing it causes serious damage, and then arguing that you can say something about the effects of dropping 0.001 kg masses on people based on the 10 kg data.

      That's not to say that it isn't plausible that dolphin sonar can be screwed up by powerful sonar, but this experiment just doesn't seem relevant to the question.

      • by INeededALogin (771371) on Wednesday April 08, 2009 @01:12PM (#27505727) Journal
        The document linked on the Bahamas stranding says that source levels were 223 - 235 dB and levels were less than 180 dB at 300 m horizontally and 200 m

        180 db is still extremely strong. Now, compound that with the fact that the Submarines are moving, pinging and that Dolphins are curious anmials and like to follow ships... and I think you will find that the chances for Dolphins being near one of these ships greatly increased.

        Also, I understand the need to defend the human race, military and blowing stuff up, but ask any blind person how much noise pollution hurts and then comment again.
        • by Kamokazi (1080091) on Wednesday April 08, 2009 @01:38PM (#27506135)

          I think you're both essentially right.

          If the dolphins were further away, the sonar would be far less damaging, but it could still interefere with their navigation.

          It's also very possible that the dolphins were following the ships and exposed to deafening decibel ranges.

          This study (like most studies) is just a stepping stone to narrow down criteria/goals for other studies...we need to A) Determine the effect of lesser decibel levels and B) Gather real observational data on how often dolphins and other marine life venture very near to naval vessels.

          Ultimately results of these studies should just regulate situations on when active sonar is used, where you can train with it, etc, because active sonar is necessary until something better is developed. Despite the very slim chances of nuclear war, as tragic as it is, I'm willing to sacrifice a few hundred sea critters (I wold hope it's a much smaller number though) just to know that we can effectively track and destroy nuclear missile subs (as well as the many other uses for sonar). That's just my opinion and you can call me a barbarian for it if you like.

        • Re: (Score:3, Insightful)

          180 db is still extremely strong. Now, compound that with the fact that the Submarines are moving, pinging and that Dolphins are curious anmials and like to follow ships... and I think you will find that the chances for Dolphins being near one of these ships greatly increased.

          A couple of things: submarines don't use active sonar if they can possibly help it - active sonar is very helpful in locating someone, but it's even more helpful in announcing your presence to everyone out to well beyond the range the

    • by Anonymous Coward on Wednesday April 08, 2009 @01:20PM (#27505869)

      Unfortunately, neither you nor I can assess what "203 decibels" means. That is because that is a meaningless phrase. Here is the information that the AFP left out:

      • Where was the 203 dB measured? Was it measured at a reference range relative to the transducer, as is common practice, or was it measured at the dolphin? This [redorbit.com] implies to me that they produced a sound equivalent to 203 dB as heard at a 40 m range, but I am just guessing.

        The difference between the reference range measurement and the receiver measurement, assuming spherical spreading (which we're likely to see at a 40m range), is 20 log r, where R is the ratio of the reference range and the receiver range. If the dolphin is 100 m away from a source emitting 203 dB at a 1 yard reference range, it will be hit with acoustic energy at 163 dB (203 - 20 log 100).

      • In what units are they working? Contrary to popular belief, decibels are not a unit, but rather a scale. Saying the dolphins were exposed to 203 dB is equivalent to saying they were exposed to 2 x 10^8. 2 x 10^8 whats? Watts? Micropascals? 20 Micropascals?

        By the way, the sound pressure levels you're accustomed to reading about as an land-lubber are probably dB//20 uPa -- i.e., measured in multiples of 20 micropascals. In underwater acoustics we almost always use dB//1 uPa -- i.e., measured in multiples of 1 micropascal. To convert from the in-air numbers to under-water numbers, add 26 dB. A 203 dB sound to an underwater physicist would be a 179 dB to an atmospheric physicist.

      Unfortunately I cannot find this article on the Biology Letters [royalsocie...ishing.org] web site to check the facts.

  • F Dolphins (Score:3, Funny)

    by scubamage (727538) on Wednesday April 08, 2009 @12:37PM (#27505243)
    Seriously, everyone knows that human wants and needs are more important than some stupid fish being able to hear. Its not like they need sound for anything.
  • You don't need to actually make dolphins deaf to know if they will be deaf! Not only is that cruel, it's unnecessary.

    It's common knowledge that exposure to 200+ decibels will make anything deaf. And this Dr. Mooney is an idiot.

    If it makes them deaf in a lab, it fucking works outside the lab!

    • by causality (777677)

      It's common knowledge that exposure to 200+ decibels will make anything deaf.

      It's common knowledge but now he's done a STUDY ("Oooooooh, Aaaaaaaah"). That means that what everybody already knew has somehow become more official!

      I think this is a new plan.

      1. Find some obvious thing that everyone already knows.
      2. Get funding to have a "study" on it.
      3. ???
      4. Profit!

      • by je ne sais quoi (987177) on Wednesday April 08, 2009 @01:12PM (#27505731)
        Actually, it hasn't been proven that the Navy's use of sonar damages these organisms, if you read the dissenting opinion [sfgate.com] from the recent supreme court decision ruling in favor of the Navy versus environmentalists, they say as much:

        Dissenting Justice Ruth Bader Ginsburg, joined by Justice David Souter, said Cooper had properly used her authority under the environmental law after finding that unrestricted sonar use could harm thousands of creatures. Instead of conducting an environmental study as the law required, or asking Congress to change the law, Ginsburg said, the Navy undermined the law with a "self-serving resort to an office in the White House" for an exemption.

        This study represents a "nail in the coffin" type of study, where it is now known unequivocally that 203 decibels will harm wildlife. To logical people, this is what's known as "proof". Knowing this, you can now measure the sound level of the Navy's sonar tests and if it's above 203 decibels, you have direct evidence that the Navy IS harming marine animals. It sounds silly and trivial, but this is how logic works sometimes, you have to prove something beyond a shadow of a doubt, and past a shadow if you want to change society.

    • > it's unnecessary.
      I'd say ears are unnecessary to navies to about the same extent that eyes are unnecessary for armies.

    • Re: (Score:2, Troll)

      by Yvanhoe (564877)
      If that can help regulate the use of military sonars who seem to not care about mass-killing dolphins, I say it is worth it.
    • I agree. This experiment is like stabbing someone with a big knife to see if they bleed. I am for sure no PETA freak - I love to hunt and 100% realize that killing animals causes them pain. But I ALREADY KNOW that shooting them with an arrow or bullet will kill them - I don't need an experiment to prove something I already know. The only thing I can think of that came out of this experiment was a dolphins threshold for hearing loss, but I have to think there are other ways to gain that knowledge.
    • I have to disagree with the validity of the statement that this carries over into the wild. Yeah, sure, if you have a dolphin tied to the side of your boat and you're sitting their blasting it with 203 decibels it'll go deaf. But do we know how quickly it drops off in strength or whether the dolphins would swim away before any lasting damage was done? Have they heard it in the past and learned to avoid naval vessels as a result? Couldn't they theoretically swim along the surface and avoid the sound altogeth
      • Couldn't they theoretically swim along the surface and avoid the sound altogether?

        Have you ever seen a Dolphin? They aren't boats. The ability to keep their ears above water for an extended period of time would consume a lot of energy if they could even do it. Also, why is it that the dolphins have to change their million years of instincts and evolution so that we can search and destroy enemy ships. On that note, when was the last time we actually had to destroy a submarine?
    • by robthebloke (1308483) on Wednesday April 08, 2009 @12:59PM (#27505557)

      It's common knowledge that exposure to 200+ decibels will make anything deaf.

      Apart from deaf people.

    • Re: (Score:2, Interesting)

      by apokruphos (911590)
      Please, cite to me the journal of "Common Knowledge". Because, as we all know, all those folksy truths always have a huge bearing on reality.
  • by TerranFury (726743) on Wednesday April 08, 2009 @12:41PM (#27505289)

    Loud noises tear the cilia in your cochlea out by the roots. In humans, and, as far as I know, other higher mammals, they don't grow back (Can someone who knows confirm that this is true in dolphins as well?).

    So the word "temporary" might make this sound less bad than it is: Our sonar may only temporarily cause total deafness, but I suspect it permanently degrades hearing.

    Sucks to be a dolphin. Reminds me of Douglas Adams' sympathy for whales, whose songs no longer can be heard across the ocean. (I think Douglas talked about this in Last Chance to See.)

    • by pembo13 (770295)

      Even if it is temporary, isn't this the equivalent of temporary blindness while on the highway?

    • by drinkypoo (153816)

      These methods are definitely cruel. On the other hand, if the research actually led to a reduction in the power of sonar systems used, then it would be worth harming a few dolphins. The problem is that if anything the research will be used to figure out the minimum sonar power required to paralyse dolphins for capture so they can be trained as mine sweepers or something.

      • by Chrontius (654879)
        Sorry, no - that's like asking what the minimum amount of light to stun a person is because you want a tac-light to use as a primary weapon. It doesn't work like that -- the answer to my question is "bright enough to ionize a thin layer of skin/clothing into an EMP-emitting plasma" and I suspect the answer to your question is "Loud enough to pulverize bone and tear nerve fibers". Problem is, both kinda cause permanent injury. Phasers don't have a magical stun setting, and you can't cause complete tempora
    • Re: (Score:3, Funny)

      by dkleinsc (563838)

      Plus if whale song isn't happening for a while, a space probe will come by and wreck everything.

  • Maybe they beached just to get away from the awful noise?

  • by yogibaer (757010) on Wednesday April 08, 2009 @12:50PM (#27505399)
    "The deafness, though, was only temporary and the dolphin was not hurt in the experiment, said Mooney." So the experiment is still cruel but obviously no permanent damage. Deafness aside: Loud noise causes disorientation and nausea in humans, so why not in dolphins. BTW: A "singing" Whale produces a sound pressure level of up to 185 dB under water! (s. http://en.wikipedia.org/wiki/Sound_pressure_level#Examples_of_sound_pressure_and_sound_pressure_levels [wikipedia.org]) So 200 sounds extreme but remember its not air we are talking about, but water. For comparison the hearing threshhold of a diver is 67dB at 1khz. The auditory threshhold through the air at 1khz is 0 dB.
  • by dAzED1 (33635) on Wednesday April 08, 2009 @01:01PM (#27505573) Homepage Journal

    My wife is a wildlife conservation researcher, and specifically works with animals in the Delphinidae family (which include dolphins). There's a lot of stuff she, and others, have to - must - verify, even if it seems to be a "wellduh."

    The alternative would be that science just thinks correlation = causation. Is that what we want? "Well, Navy ships used sonar, and these whales stranded themselves...must be related. Case closed." Instead, someone did actual science showing that sonar causes real deafness in these animals. And someone wants to harsh that?

    I say instead that there should be a tag, "abouttimetheyverified"

    • by tnk1 (899206)

      Science is only useful to some people when it aligns with their sensibilities. That goes for pretty much all sides of whatever debate you are in.

      In this case, the point is that they would rather not risk any dolphin be hurt to get a scientific answer. That's actually a fair position, as it is the one we take with humans.

      That said, the Navy isn't just testing SONAR for shits and giggles, and you can be certain that the Chinese and Russians don't give a shit about dolphins. That means that it's necessary f

  • by ericferris (1087061) on Wednesday April 08, 2009 @01:05PM (#27505623) Homepage

    Classic Greek authors tell us that in the ancient Greece, dolphins and whales were already found stranded on the shore. This was a windfall for the locals, who were not eating meat very often. They saw it as a divine gift and thanked Poseidon for it.

    So considering that the Greek galleys didn't use sonar, we need to stop barking at the wrong tree and find the cause of this phenomenon. My money is on a parasitic disease that affects the brain [caltech.edu].

    • Re: (Score:3, Funny)

      Classic Greek authors tell us that in the ancient Greece, dolphins and whales were already found stranded on the shore. This was a windfall for the locals, who were not eating meat very often. They saw it as a divine gift and thanked Poseidon for it. So considering that the Greek galleys didn't use sonar, we need to stop barking at the wrong tree and find the cause of this phenomenon.

      Unless, of course, there was a sonar-equipped sub from Atlantis somewhere nearby... Or submerged alien vessels.

      • Yeah, well, that's the kind of assumptions you need to make if you want to keep blaming the sonar of the *EVIL MILITARY* (thunder rolls).

        The arrogance of every young generations is to believe all problems on Earth are created by their parents' incompetence. Get a haircut and a bath, you hippies!

    • by raddan (519638) on Wednesday April 08, 2009 @01:34PM (#27506063)
      Or maybe the causes of stranding are a many-to-one relation, i.e., that there is more than one cause, and that use of sonar is only one of them. E.g., you find dead birds with broken necks all the time. It is disingenuous to say that windows are the cause of all broken bird necks, and we can point out that people have found dead birds with broken necks even in antiquity. But it is equally disingenuous to say that windows have nothing to do with it.
      • Re: (Score:3, Insightful)

        by MRe_nl (306212)

        Remember: this is /.
        So please stop making complete and utter sense.
        But continue blaming Windows.

        And it's bark "UP" the wrong tree, not "AT", OP.

    • by qw0ntum (831414)

      From the summary:

      Most strandings are still thought to be natural events, but the tests strengthen fears that exercises by naval vessels equipped with sonar are responsible for at least some of them.

      No one said that strandings aren't a natural phenomenon. They have multiple causes! You didn't even have to click a link to see that!

    • Re: (Score:3, Funny)

      by OolimPhon (1120895)

      So considering that the Greek galleys didn't use sonar

      [Citation needed]

  • Excellent (Score:2, Interesting)

    by proxy318 (944196)
    Now we have a new weapon for the inevitable dolphin uprising.
  • by Reverberant (303566) on Wednesday April 08, 2009 @01:08PM (#27505673) Homepage

    WRT to all of the "203 decibels, OMG!" comments: water decibels aren't the same as SPL decibels.

    A decibel is the logarithmic relationship between one quantity and a reference quantity. For sound pressure level, we use the RMS pressure of the sound wave compared to a reference pressure that represents the threshold of human hearing (20 microPa): 20*Log10(P/20e-6)

    Other types of decibels use different reference quantities. For example, vibration velocity in the USA uses a reference quantify of 10^-6 in/sec. Sound intensity (sound power through a unit area) uses a reference quantity of 10^-12 W/m2. So comparing sad sound intensity decibels to vibration velocity decibels is meaningless without normalizing the units.

    In the case of water decibels, we use pressure as we do for SPL in air, but the reference quantity is different: for water, the reference quantity is typically 1 microPa. Therefore the 203 dB in water is approximately equivalent to about 170 dB SPL in air. Of course you still can't directly compare water dB to SPL because the wavelengths of sound in water are so much longer than wavelengths of sound in air.

    In any event, 203 dB in water is very loud (and obviously harmful to aquatic life as demonstrated in the articles), but not necessarily in the same way that 173 dB SPL is loud/harmful to us.

  • It's a good thing this affects dolphins instead of sharks. What platform would we use for our lasers if sharks were this easy to mess up?

  • ...now when they come for us, we'll be ready.

  • It seems that the Navy may be pursuing the wrong solution to increasing sonar range and resolution. Rather than increasing the transmit power to such levels, perhaps more sensitive receivers are needed. Whales and dolphins echo location capabilities exceed the current capabilities of Navy equipment and they don't need any 200db or more power outputs.

    It is believed that whales can communicate over hundreds of miles. Such levels of sensitivity also lend themselves to passive detection (for the Navy) which is

  • by DaveV1.0 (203135) on Wednesday April 08, 2009 @02:23PM (#27506869) Journal

    To induce deafness in the Atlantic bottlenose dolphin, Tursiops truncatus, the sonar device would have to be loud, close and would need to last for at least two minutes.

    To the best of my knowledge, SONAR is short bursts of loud noise broken by longer periods of quiet to receive and process the return echos. Two minutes of continuous sound is not going to happen. Even if the effect is cumulative, a cetacean would have to travel with the source for over five minutes which it is unlikely to do if the SONAR is injurious. Would you hang out in an excruciatingly loud environment?

    Now, some will point to this:Sound can become trapped if a layer of warm water lies over cold water. When sound created in the warm zone reaches the cold water it can bounce back instead of travelling though it. This, Dr Mooney said, would have the effect of trapping the sound in the warm layer, where it would bounce around "like a ping-pong ball", giving whales and dolphins little chance of escaping it.

    But, the thing is, dolphins and whales are mammals. The would leave the noisy layer when they surfaced. Therefore, they would quickly learn how to escape the sound: surface or dive.

    The conclusions seem specious to me.

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