Marine mammals and sonar - AbsoluteAstronomy.com

Active sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

, the transmission equipment used on some ships to assist with navigation

Navigation

Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...

, has been suggested to be detrimental to the health and livelihood of some marine animals, although the precise mechanisms for this are not well understood. Some marine animals, such as whale

Whale

Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...

s and dolphin

Dolphin

Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...

s, use echolocation

Animal echolocation

Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...

or "biosonar" systems to locate predators and prey. It is conjectured that active sonar transmitters could confuse these animals and interfere with basic biological functions such as feeding and mating. A recent study has shown that whales experience decompression sickness, a disease that forces nitrogen into gas bubbles in the tissues and is caused by rapid and prolonged surfacing. Although whales were originally thought to be immune to this disease, sonar has been implemented in causing behavioral changes that can lead to decompression sickness.

History

The SOFAR channel
Sofar channel
The SOFAR channel , or deep sound channel , is a horizontal layer of water in the ocean at which depth the speed of sound is minimal. The SOFAR channel acts as a waveguide for sound, and low frequency sound waves within the channel may travel thousands of miles before dissipating...

(short for sound fixing and ranging channel), or deep sound channel (DSC), is a horizontal layer of water in the ocean centered around the depth at which the speed of sound

Speed of sound

The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In dry air at , the speed of sound is . This is , or about one kilometer in three seconds or approximately one mile in five seconds....

is at a minimum. The SOFAR channel acts as a waveguide

Waveguide

A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...

for sound, and low frequency sound waves

Underwater acoustics

Underwater acoustics is the study of the propagation of sound in water and the interaction of the mechanical waves that constitute sound with the water and its boundaries. The water may be in the ocean, a lake or a tank. Typical frequencies associated with underwater acoustics are between 10 Hz and...

within the channel may travel thousands of miles before dissipating. This phenomenon is an important factor in submarine warfare

Submarine warfare

Naval warfare is divided into three operational areas: surface warfare, air warfare and underwater warfare. The latter may be subdivided into submarine warfare and anti-submarine warfare as well as mine warfare and mine countermeasures...

. The deep sound channel was discovered and described independently by Dr. Maurice Ewing

Maurice Ewing

William Maurice "Doc" Ewing was an American geophysicist and oceanographer.Ewing has been described as a pioneering geophysicist who worked on the research of seismic reflection and refraction in ocean basins, ocean bottom photography, submarine sound transmission , deep sea coring of the ocean...

, and Leonid Brekhovskikh

Leonid Brekhovskikh

Leonid Maksimovich Brekhovskikh was a Russian/Soviet scientist known for his work in acoustical and physical oceanography.-Life:...

in the 1940s.

Despite the use of the SOFAR channel

Sofar channel

The SOFAR channel , or deep sound channel , is a horizontal layer of water in the ocean at which depth the speed of sound is minimal. The SOFAR channel acts as a waveguide for sound, and low frequency sound waves within the channel may travel thousands of miles before dissipating...

in naval applications, the idea that animals might make use of this channel was not proposed until 1971. Roger Payne

Roger Payne

Roger Searle Payne is a biologist and environmentalist famous for the 1967 discovery of Whale song among Humpback whales. Payne later became an important figure in the worldwide campaign to end commercial whaling.Payne studied at Harvard University and Cornell...

and Douglas Webb calculated that before ship traffic noise permeated the oceans, tones emitted by fin whales could have traveled as far as four thousand miles and still be heard against the normal background noise of the sea. Payne and Webb further determined that, on a quiet day in the pre–ship-propeller oceans, fin whale tones would only have fallen to the level of background noise

Background noise

In acoustics and specifically in acoustical engineering, background noise or ambient noise is any sound other than the sound being monitored. Background noise is a form of noise pollution or interference. Background noise is an important concept in setting noise regulations...

after traveling thirteen thousand miles, that is, more than the diameter

Diameter

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...

of the Earth.

Early confusion between fin whales and military sonar

Before extensive research on whale echolocation

Animal echolocation

was completed, the low-frequency pulses emitted by some species of whales were often not correctly attributed to them. Dr Payne wrote:"Before it was shown that fin whales were the cause [of powerful sonar transmissions], no one could take seriously the idea that such regular, loud, low, and relatively pure frequency tones were coming from within the ocean, let alone from whales." This unknown sound was popularly known by navy acousticians as the Jezebel Monster. (Jezebel was narrow-band passive long-range sonar.) Some researchers believed that these sounds could be attributed to geophysical vibrations or an unknown Russian military program, and it wasn't until biologists William Schevill and William A. Watkins proved that whales possessed the biological capacity to emit sonar that the unknown sounds were correctly attributed.

Low frequency sonar

The electromagnetic spectrum

Electromagnetic spectrum

The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....

has rigid definitions for "super low frequency", "extremely low frequency", "low frequency" and "medium frequency". Acoustics

Acoustics

Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics...

does not have a similar standard. The terms "low" and "mid" have roughly-defined historical meanings in sonar, because not many frequencies have been used over the decades. However, as more experimental sonars have been introduced, the terms have become muddled.

American low frequency sonar was originally introduced to the general public in a June 1961 Time magazine article, New A.S.W.ASW is an acronym for "anti-submarine warfare" Artemis

Project ARTEMIS

Project ARTEMIS was a project undertaken by the United States Navy in the 1960s, which produced a Low Frequency Active Sonar system that could detect submarines at long range. Robert A. Frosch, in his capacity as Technical Director of Hudson Laboratories , was Technical Director of the project. Dr....

, the low-frequency sonar used at the time, could fill a whole ocean with searching sound and spot anything sizable that was moving in the water. Artemis grew out of a 1951 suggestion by Harvard physicist

Physicist

A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

Frederick V. Hunt (Artemis

Artemis

Artemis was one of the most widely venerated of the Ancient Greek deities. Her Roman equivalent is Diana. Some scholars believe that the name and indeed the goddess herself was originally pre-Greek. Homer refers to her as Artemis Agrotera, Potnia Theron: "Artemis of the wildland, Mistress of Animals"...

is the Ancient Greek

Ancient Greek

Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

goddess of the hunt), who convinced Navy anti-submarine experts that submarines could be detected at great distances only by unheard-of volumes of low-pitched sound.
At the time, an entire Artemis system was envisioned to form a sort of underwater DEW (Distant Early Warning) line to warn the U.S. of hostile submarines. Giant, unattended transducers, powered by cables from land, would be lowered to considerable depths where sound travels best. The Time magazine article was published during the maiden voyage

Maiden voyage

The maiden voyage of a ship, aircraft or other craft is the first journey made by the craft after shakedown. A number of traditions and superstitions are associated with it....

of the Soviet submarine K-19

Soviet submarine K-19

K-19, KS-19, BS_19 was one of the first two Soviet submarines of the 658, 658м, 658с class , the first generation nuclear submarine equipped with nuclear ballistic missiles, specifically the R-13 . Its keel was laid down on 17 October 1958, christened on 8 April 1959 and launched on 11 October 1959...

, which was the first Soviet submarine equipped with ballistic missiles. Four days later the submarine would have the accident that gave it its nickname. The impact on marine mammals by this system was certainly not a consideration. Artemis never became an operational system.

Low-frequency sonar was revived in the early 1980s for military and research applications. The idea that the sound could interfere with whale biologics became widely discussed outside of research circles when Scripps Institute of Oceanography borrowed and modified a military sonar for the Heard Island Feasibility Test conducted in January and February 1991. The sonar modified for the test was an early version of SURTASS deployed in the MV Cory Chouest

MV Cory Chouest

MV Cory Chouest is an ocean surveillance ship leased by the U.S. Navy in 1989 and assigned to the Navy’s Special Missions Program. Cory Choquest had all SURTASS equipment removed and was returned to her original owners in 2008 completing nearly 20 years of service.-Construction:Cory Chouest was...

. As a result of this test a "Committee on Low-Frequency Sound and Marine Mammals" was organized by the National Research Council

United States National Research Council

The National Research Council of the USA is the working arm of the United States National Academies, carrying out most of the studies done in their names.The National Academies include:* National Academy of Sciences...

. Their findings were published in 1994, in Low-Frequency Sound and Marine Mammals: Current Knowledge and Research Needs.

Long-range transmission does not require high power. All frequencies of sound lose an average of 65dB

Decibel

The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...

in the first few seconds before the sound waves strike the ocean bottom. After that the acoustic energy in mid or high-frequency sound is converted into heat, primarily by the epsom salt dissolved in sea water. Very little of low frequency acoustic energy is not converted into heat, so the signal can be detected for long ranges. Fewer than five of the transducers from the low frequency active array were used in the Heard Island Feasibility Test, and the sound was detected on the opposite side of the Earth. The transducers were temporarily altered for this test to transmit sound at 50 hertz

Hertz

The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....

, which is lower than their normal operating frequency.

A year after the Heard Island Feasibility Test a new low-frequency active sonar was installed in the Cory Chouest with 18 transducers instead of 10. An environmental impact statement

Environmental impact statement

An environmental impact statement , under United States environmental law, is a document required by the National Environmental Policy Act for certain actions "significantly affecting the quality of the human environment". An EIS is a tool for decision making...

was prepared for that system.

Mid frequency sonar

The term mid frequency sonar is usually used to refer to sonars that project sound in the 3 to 4 kilohertz (kHz) range. Ever since the launch of the on 17 January 1955 the US Navy knew it was only a matter of time until the other naval powers had their own nuclear submarines. The mid-frequency sonar was developed for anti-submarine warfare

Anti-submarine warfare

Anti-submarine warfare is a branch of naval warfare that uses surface warships, aircraft, or other submarines to find, track and deter, damage or destroy enemy submarines....

against these future boats. The standard post-WWII active sonars (which were usually above 7 kHz) had an insufficient range against this new threat. Active sonar went from a piece of equipment attached to a ship, to a piece of equipment that was central to the design of a ship. They are described in the same 1961 Time magazine article by the quote "the latest shipboard sonar weighs 30 tons and consumes 1,600 times as much power as the standard postwar sonar". A modern system produced by Lockheed Martin

Lockheed Martin

Lockheed Martin is an American global aerospace, defense, security, and advanced technology company with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It is headquartered in Bethesda, Maryland, in the Washington Metropolitan Area....

since the early 1980s is the AN/SQQ-89. On June 13, 2001, Lockheed Martin announced that it had delivered its 100th AN/SQQ-89 undersea warfare system to the U.S. Navy.

There was anecdotal evidence

Anecdotal evidence

The expression anecdotal evidence refers to evidence from anecdotes. Because of the small sample, there is a larger chance that it may be true but unreliable due to cherry-picked or otherwise unrepresentative of typical cases....

that mid-frequency sonar could have adverse effects on whales dating back to the days of whaling. The following story is recounted in a book published in 1995:

Mid Frequency Sonar and Whaling
Source: Among Whales by Roger Payne (pg 258) Published 2 June 1995
Another innovation by the whalers was the use of sonar to track whales they were pursuing underwater. But there was a problem; as the boat gained on the whale, the whale started exhaling while still submerged. This produced a cloud of bubbles in the water that reflected sound better than the whale did and made a false target (akin to what a pilot does when releasing metal chaff to create a false radar echo). I suspect that this behavior by whales was simply fortuitous since exhaling while still submerged is simply a means by which a whale can reduce the time it has to remain at the surface, where surface drag will slow it down. Whalers quickly discovered that a frequency of three thousand hertz seemed to panic the whales, causing them to surface much more often for air, This was a “better" use for sonar because it afforded the whalers more chances to shoot the whales. So they equipped their catcher boats with sonar at that frequency. Of course the sonar also allows the whalers to follow the whale underwater, but that is its secondary use. Its primary use is for scaring whales so that they start “panting” at the surface.

In 1996 twelve Cuvier's beaked whale

Cuvier's Beaked Whale

Cuvier's beaked whale is the most widely distributed of all the beaked whales. It is the only member of the genus Ziphius. Another common name for the species is goose-beaked whale because its head is said to be shaped like the beak of a goose. Georges Cuvier first described it in 1823 from part...

s beached themselves alive along the coast of Greece

Greece

Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....

while NATO (North Atlantic Treaty Organisation) was testing an active sonar with combined low and mid-range frequency transducers, according to a paper published in the journal Nature

Nature

Nature, in the broadest sense, is equivalent to the natural world, physical world, or material world. "Nature" refers to the phenomena of the physical world, and also to life in general...

in 1998. The author established for the first time the link between atypical mass strandings of whales and the use of military sonar by concluding that although pure coincidence cannot be excluded there was better than a 99.3% likelihood that sonar testing caused that stranding. He noted that the whales were spread along 38.2 kilometres of coast and were separated by a mean distance of 3.5 km (sd=2.8, n=11). This spread in time and location was atypical, as usually whales mass strand at the same place and at the same time.

At the time that Dr. Frantzis wrote the article he was unaware of several important factors.

The time correlation was much tighter than he knew. He knew about the test from a notice to mariners which only published that the test would occur over a five day period within a large area of the ocean. In fact the first time the sonar was turned on was the morning of 12 May 1996, and six whales stranded that afternoon. The next day the sonar was turned on again and another six whales stranded that afternoon. Without knowing the coordinates of the ships he would not have realized that the ship was only about 10–15 miles offshore.
The sonar being used in the test was an experimental research and development sonar, which was considerably smaller and less powerful than an operational sonar onboard a deployed naval vessel. Dr Frantzis believed that wide distribution of the stranded whales indicated that the cause has a large synchronous spatial extent and a sudden onset. Knowing that the sound source level was fairly low (it was only 226 dB (decibels) @ 3 kHz which is low compared to an operational sonar) would have made the damage mechanism even more puzzling.
The experimental sonar used in the test, Towed Vertically Directive Source (TVDS) which had the dual 600 Hz and 3 kHz transducers, had been used for the first time in the Mediterranean Sea south of Sicily the year before in June 1995. Previous activated towed array sonar research using different sources on board the same ship included participation in NATO exercises "Dragon Hammer '92" and "Resolute Response '94".

Since the source level of this experimental sonar was only 226 dB @ 3 kHz re. 1 meter, at only 100 meters the received level would drop by 40 dB (to 186 dB). A NATO panel investigated the above stranding and concluded the whales were exposed to 150-160 dB re 1 μPa of low and mid-range frequency sonar. This level is about 66 dB less (more than a million times lower intensity) than the threshold for hearing damage specified by a panel of marine mammal experts.

The idea that a relatively low power sonar could cause a mass stranding of such a large number of whales was very unexpected by the scientific community. Most research had been focused on the possibility of masking signals, interference with mating calls, and similar biological functions. Deep diving marine mammals were species of concern, but very little definitive information was known. In 1995 a comprehensive book on the relation between marine mammals and noise had been published, and it did not even mention strandings.

Acoustically induced bubble formation

There was anecdotal evidence from whalers (see section above) that sonar could panic whales and cause them to surface more frequently making them vulnerable to harpooning. It has also been theorized that military sonar may induce whales to panic and surface too rapidly leading to a form of decompression sickness

Decompression sickness

Decompression sickness describes a condition arising from dissolved gases coming out of solution into bubbles inside the body on depressurization...

. In general trauma caused by rapid changes of pressure is known as barotrauma. The idea of acoustically enhanced bubble formation was first raised by a paper published in The Journal of the Acoustical Society of America in 1996 and again Nature in 2003. It reported acute gas-bubble lesions (indicative of decompression sickness) in whales that beached shortly after the start of a military exercise off the Canary Islands

Canary Islands

The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...

in September 2002.

In the Bahamas in 2000, a sonar trial by the United States Navy

United States Navy

The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

of transmitters in the frequency range 3–8 kHz

Hertz

at a source level of 223–235 decibels re 1 μPa (scaled to a distance of 1 m) was associated with the beaching of seventeen whales, seven of which were found dead. Environmental groups claimed that some of the beached whales were bleeding from the eyes and ears, which they considered an indication of acoustically-induced trauma. The groups allege that the resulting disorientation may have led to the stranding.

Naval sonar-linked incidents

Date	Location	Species and Number	Naval Activity
1963-05	Gulf of Genoa Gulf of Genoa The Gulf of Genoa is the northernmost part of the Ligurian Sea. The width of the gulf is about 125 km, from the city of Imperia in the west to La Spezia in the east. The largest city on the its coast is Genoa, which has an important port.... , Italy Italy Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...	Cuvier’s beaked whale (15) stranded	Naval maneuvers
1988-11	Canary Islands Canary Islands The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...	Cuvier’s beaked whale (12+) Gervais' beaked whale (1) stranded	FLOTA 88 exercise
1989-10	Canary Islands Canary Islands The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...	Cuvier's beaked whale (15+), Gervais' beaked whale (3), Blainville's beaked whale (2) stranded	CANAREX 89 exercise
1991-12	Canary Islands Canary Islands The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...	Cuvier's beaked whale (2) stranded	SINKEX 91 exercise
1996-05-12	Gulf of Kyparissia Gulf of Kyparissia The Gulf of Kyparissia is a long, curving indentation along the western coast of the Peloponnese peninsula, Greece. It lies between Cape Katakolo at the north end and Cape Konello to the south. Near the northern extreme is the city of Pyrgos, with the town of Zacharo near the center and the town... , Greece Greece Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....	Cuvier's beaked whale (12) stranded	NATO Shallow Water Acoustic Classification exercise
1998-07	Kauai Kauai Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",... , Hawaii Hawaii Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...	beaked whale (1), sperm whale (1) stranded	RIMPAC RIMPAC RIMPAC, the Rim of the Pacific Exercise, is the world's largest international maritime exercise. Conducted biennially , it is hosted and administered by the United States Navy, with the United States Marine Corps, United States Coast Guard, and Hawaii National Guard forces under the leadership of... 98 exercise
1999-10	U.S. Virgin Islands and Puerto Rico Puerto Rico Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...	Cuvier’s beaked whale (4) stranded	COMPTUEX Composite Unit Training Exercise COMPTUEX, or Composite Training Unit Exercise, is a rehearsal each US Navy Carrier Strike Group performs before departing for deployment. Each ship and aircraft in the battle group trains in its speciality, COMPTUEX brings ships together to project force as a battle group... exercise
2000-03-15	Bahamas	Cuvier’s beaked whale (9), Blainville’s beaked whale (3), beaked whale spp (2), Minke whale (2), Atlantic spotted dolphin (1) stranded	Naval MFA
2000-05-10	Madeira Island, Portugal Portugal Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...	Cuvier’s beaked whale (3) stranded	NATO Linked Seas 2000 and MFA
2002-09	Canary Islands Canary Islands The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...	Cuvier’s beaked whale (9), Gervais’ beaked whale (1), Blainville’s beaked whale (1), beaked whale spp. (3) stranded	Neo Tapon 2002 exercise and MFA
2003-05	Haro Strait Haro Strait Haro Strait, often referred to as the Haro Straits because it is really a series of straits, is one of the main channels connecting the Strait of Georgia to the Strait of Juan de Fuca, separating Vancouver Island and the Gulf Islands in British Columbia, Canada from the San Juan Islands of... , Washington	Harbor porpoise (14), Dall’s porpoise (1) Orca avoidance “stampede”	U.S.S. Shoup USS Shoup (DDG-86) USS Shoup is an Arleigh Burke-class destroyer in the United States Navy. The ship is named for General David M. Shoup , the 22nd Commandant of the Marine Corps.... transiting while using MFA (AN/SQS-53C)
2004-07	Kauai Kauai Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",... , Hawaii Hawaii Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...	Melon-headed whale (~200) avoidance “stampede”	RIMPAC RIMPAC RIMPAC, the Rim of the Pacific Exercise, is the world's largest international maritime exercise. Conducted biennially , it is hosted and administered by the United States Navy, with the United States Marine Corps, United States Coast Guard, and Hawaii National Guard forces under the leadership of... 04 exercise with MFA
2004-07-22	Canary Islands Canary Islands The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...	Cuvier’s beaked whale (4) stranded	Majestic Eagle 04 exercise
2005-10-25	Marion Bay Marion Bay, Tasmania Marion Bay is a large bay and a bounded locality located on the southeast coast of Tasmania, Australia. It is near Dunalley in the Municipality of Sorell... , Tasmania Tasmania Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...	Long-finned pilot whales (145) stranded	Two minesweepers using active sonar
2006-01-26	Almeira Coast, Spain Spain Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...	Cuvier's beaked whale (4) stranded	Royal Navy’s HMS Kent HMS Kent (F78) HMS Kent is a Type 23 Duke class frigate of the British Royal Navy, and the twelfth ship to bear the name.Kents lineage boasts sixteen Battle Honours from the three given to the first Kent of 46 guns built in 1653, to the five awarded to the ninth and tenth Kents of World War I and World War... using active sonar
2008-06	Cornish coast, United Kingdom United Kingdom The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...	Dolphins (26) stranded	Royal Navy sonar exercise

Court cases

Since mid-frequency sonar has been correlated with mass cetacean strandings throughout the world's oceans, it has been singled out by some environmentalists as a focus for activism. A lawsuit filed by the Natural Resources Defense Council

Natural Resources Defense Council

The Natural Resources Defense Council is a New York City-based, non-profit, non-partisan international environmental advocacy group, with offices in Washington DC, San Francisco, Los Angeles, Chicago, and Beijing...

(NRDC) in Santa Monica, California

Santa Monica, California

Santa Monica is a beachfront city in western Los Angeles County, California, US. Situated on Santa Monica Bay, it is surrounded on three sides by the city of Los Angeles — Pacific Palisades on the northwest, Brentwood on the north, West Los Angeles on the northeast, Mar Vista on the east, and...

on 20 October 2005 contended that the U.S. Navy has conducted sonar exercises in violation of several environmental laws, including the National Environmental Policy Act

National Environmental Policy Act

The National Environmental Policy Act is a United States environmental law that established a U.S. national policy promoting the enhancement of the environment and also established the President's Council on Environmental Quality ....

, the Marine Mammal Protection Act

Marine Mammal Protection Act

The Marine Mammal Protection Act of 1972 was the first article of legislation to call specifically for an ecosystem approach to natural resource management and conservation. MMPA prohibits the taking of marine mammals, and enacts a moratorium on the import, export, and sale of any marine mammal,...

, and the Endangered Species Act

Endangered Species Act

The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...

. Mid-frequency sonar is by far the most common type of active sonar in use by the world's navies, and has been widely deployed since the 1960s.

On November 13, 2007, a United States appeals court restored a ban on the U.S. Navy's use of submarine-hunting sonar in training missions off Southern California until it adopted better safeguards for whales, dolphins and other marine mammals. On 16 January 2008, President George W. Bush exempted the US Navy from the law and argued that naval exercises are crucial to national security. On 4 February 2008, a Federal judge ruled that despite President Bush's decision to exempt it, the Navy must follow environmental laws placing strict limits on mid-frequency sonar. In a 36-page decision, U.S. District Judge Florence-Marie Cooper wrote that the Navy is not "exempted from compliance with the National Environmental Policy Act" and the court injunction creating a 12 nautical miles (22.2 km) no-sonar zone off Southern California. On 29 February 2008, a three-judge federal appeals court panel upheld the lower court order requiring the Navy to take precautions during sonar training to minimize harm to marine life. In Winter v. Natural Resources Defense Council
Winter v. Natural Resources Defense Council
Winter v. Natural Resources Defense Council, 555 U.S. 7 , was a case heard before the United States Supreme Court on October 8, 2008 concerning the United States Navy ability to use sonar during drills causing possible harm to whales and other marine mammals.In balancing military preparedness...

. the U.S. Supreme Court overturned the circuit court ruling in a 5:4 decision on 12 November 2008.

Mitigation methods

Environmental impacts of the operation of active sonar are required to be carried out by US law. Procedures for minimising the impact of sonar are developed in each case where there is significant impact.

The impact of underwater sound can be reduced by limiting the sound exposure

Noise dosimeter

A noise dosimeter or noise dosemeter is a specialized sound level meter intended specifically to measure the noise exposure of a person integrated over a period of time; usually to comply with Health and Safety regulations such as the Occupational Safety and Health or EU Directive 2003/10/EC.-...

received by an animal. The maximum sound exposure level recommended by Southall et al. for cetaceans is 215 dB re 1 μPa² s for hearing damage. Maximum sound pressure level for behavioural effects is dependent on context (Southall et al.).

A great deal of the legal and media conflict on this issue has to do with questions of who determines what type of mitigation is sufficient. Coastal commissions, for example, were originally thought to only have legal responsibility for beachfront property, and state waters (three miles into sea). Because active sonar is instrumental to ship defense, mitigation measures that may seem sensible to a civilian agency without any military or scientific background can have disastrous effects on training and readiness. Navies therefore often define their own mitigation requirements.

Examples of mitigation measures include:

not operating at nighttime
not operating at specific areas of the ocean that are considered sensitive
slow ramp-up of intensity of signal to give whales a warning
air cover to search for mammals
not operating when a mammal is known to be within a certain range
onboard observers from civilian groups
using fish-finders to look for whales in the vicinity
large margins of safety for exposure levels
not operating when dolphins are bow-riding
operations at less than full power
paid teams of veterans to investigate strandings after sonar operation.

Besides the expense of some of the mitigation measures some of them might interfere with operations. For this reason, mitigation requirements for wartime use of naval sonars can differ from either civilian mitigation requirements or from military requirements during exercises or peacetime operations. Prohibition on night time operations may be a huge waste of expensive assets. Ramping up a signal in intensity may have no impact on geophysical operations, but sonar does not work very well if you give the target submarine a warning so that he can do countermeasures. On board civilian observers are used in tuna-boat operations, and in dredging exercises, which are radically different from military operations.

External links

Research by Antonella Servidio in a German TV Documentary by Volker Barth
Studying Sonar's Effects on Marine Mammals Blog Post on the Smithsonian Ocean Portal

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