Glossary

the most commonly used frequency weighting function for humans that accounts for the fact that human hearing is less sensitive to low frequencies; units dB(A) or dBA.

the conversion of acoustic energy to heat energy

the rate of change of velocity with respect to magnitude or direction.

a device that measures the vibration, or change in motion (acceleration) of a structure or organism. The force caused by vibration or a change in motion causes piezoelectric material within the device to be squeezed, which produces an electrical charge that is proportional to the force exerted upon it. Since the charge is proportional to the force, and mass remains constant, the charge is also proportional to the acceleration.

the degree of closeness of measurements of a quantity to its actual value.

the composite of all sounds in an environment. The perception of the acoustic environment for each animal will vary depending on its hearing abilities.

a transmitter implanted or attached to a fish to monitor fish movement

the amount of sound pressure generated by a given vibration at a specific frequency.

a statistic that summarizes several aspects of the distribution of acoustic energy and information.  Acoustic indices have been developed to estimate characteristics of the acoustic production of biological communities including richness and heterogeneity.

a wireless communication device used to transmit data and information through the ocean

conceptual and numerical models that compute how sound travels through the water, taking into account many variables such as water temperature, salinity, bottom topography, etc.

a device which holds onto the anchor of a buoyant instrument until it is commanded to release it

acoustic characteristics or attributes of a sound source that can be used for its identification.

to transmit acoustic signals automatically and at a distance, as between a ground station and an artificial satellite, space probe, or the like, especially in order to record information, operate guidance apparatus, etc

the received level at which an effect from acoustic exposure may begin to occur.

uses the travel time of sound in the ocean to measure the temperature of the ocean over large areas

severe traumatic injury from sound

a condition that occurs when refraction or reflection prevents direct sound waves from reaching a region (called a shadow zone)

sound is purposefully generated and received

an alteration in the structure or function of an organism or any of its parts that results in the organism becoming better fitted to survive and multiply in its environment.

Acoustic Doppler Current Profiler; an instrument used to measure the current using acoustic sound and the knowledge of the Doppler effect

aggressive or defensive social interaction (such as fighting, fleeing, or submitting) between individuals usually of the same species

An airgun is designed to release compressed air, which forms bubbles. The formation of bubbles produces a loud sound that is used to explore the geologic structure of the ocean floor. Airguns primarily produce sound at low frequencies (between 10-500 Hz); however, high frequency noise is also created. A small airgun that releases 0.16 Liters of air can create source amplitudes up to 216 underwater dB at 1 meter. A large airgun that releases 32.8 Liters of air can have a source level of up to 232 underwater dB at 1 meter.

a step-by-step procedure for calculations/solving a problem.

A surface current that flows parallel to the shore.

Inia geoffrensis

background sound in the ocean. Examples of sound sources contributing to ambient noise include waves, wind, rain, shrimp, earthquakes, volcanoes, and distant sources, such as shipping and airguns.

Homarus americanus

Alosa sapidissima

living or able to live on land and in the water

the maximum distance that a vibrating particle moves from its equilibrium; how much the medium is disturbed

fish that are born in fresh water, migrate to the ocean to grow into adults, and return to fresh water to spawn.

a weather instrument that measures wind speed.

the angle that the incident wave makes with a line perpendicular or normal to the reflecting surface

the angle that the reflected wave makes with a line perpendicular or normal to the reflecting surface

An animated frequency spectrum is a series of frequency spectra that show just the frequencies present at each moment in time. You can see what frequencies are associated with each part of a sound.

Balaenoptera bonaerensis

caused by humans

claw-like mouth on a sea urchin that contains five calcium carbonate teeth that are used for feeding

a single hydrophone in a receiving array or a single projector (sound source) in a projector array

invertebrates of the phylum Arthropoda that have jointed appendages and a chitinous, segmented exoskeleton. Arthropods include insects, spiders, crabs, and lobsters.

Micropogonias undulatus

Scomber scombrus

Salmo salar

Stenella frontalis

a deep-water laboratory located in the Bahamas (in the Tongue of the Ocean (TOTO)) that is instrumented with a variety of acoustic beacons and sensors to provide testing, evaluation, and certification for U.S. Navy submarine captains and their crews, as well as the accuracy of their undersea weapons. A Marine Mammal Monitoring (M3R) system has been established at AUTEC to monitor vocalizing animals via the 91 range hydrophones.

the decrease in the intensity of a wave due to the loss of acoustic energy to heat energy

a graph expressing hearing loss (hearing sensitivity) as a function of frequency

a graph displaying the range of sounds that humans can hear.

Whenever a sound wave is detected by the ear, it triggers a number of neuro-physiological responses along the auditory pathway. An auditory brainstem response test is an objective test that measures the electrical potential produced in response to sound stimuli by the synchronous discharge of the first through sixth order neurons in the auditory nerve and brainstem. Also sometimes known as brainstem auditory evoked potential (BAEP) or brainstem auditory evoked response (BAER).

a hollow, bony structure that encloses parts of the middle and inner ear.

when the intensity level or duration of sound overwhelms the hair cells so they cannot respond to sounds appropriately

an air-filled canal that leads from the ear flap to the ear drum. It helps direct sound waves to the ear drum.

the sensory system for hearing, consisting of the ear and the central nervous system.

a mathematical equation that compensates for the fact that animals do not hear equally well at all frequencies.

southern hemisphere

Cherax destructor

an automated tracking system used to electronically identify and locate ships. AIS uses GPS-linked, very high frequency radio signals that allow for ship-to-ship and ship-to-shore information transfer. Information transmitted includes a ship's name, position, speed, heading, and other information. These details are transmitted multiple times each minute.

existing and/or functioning independently; with regards to underwater vehicles, one which travels underwater without requiring input from an operator.

folded muscle segments that, when contracted, produce a wavelike motion that moves the fish through the water

the deflection of sound in a scattering process through an angle greater than 90 degrees. Backscatter is the term commonly used to describe the return of sound from the seafloor to the receiver in an active sonar.

Lipotes vexillifer

series of horny plates that hang from the gums of the upper jaw of some large whales (called Mysticetes). The baleen is made from the same materials as human hair and fingernails. It is used to filter small bits of food from the water.

These large cetaceans are usually more than 9.1 m (30 ft) long and can be found throughout the ocean. Instead of teeth, mysticetes have a series of horny plates called baleen. The baleen is made from the same materials as human hair and fingernails. The baleen plates hang from the gums of the upper jaw and are used to filter small bits of food from the water. Baleen whales have symmetrical skulls and have two (or paired) blowholes.The mysticetes are divided into four families: rorquals (blue, humpback, minke, sei, fin, and Bryde's whales), right whales, pygmy right whales, and gray whales. Rorquals have throat pleats, or ventral grooves, that expand when the whales gulp large amounts of water during feeding. Baleen whales can migrate up to hundreds of miles to feed in cooler areas with lots of food. On the feeding grounds baleen whales filter out small organisms from the water either by skimming the surface or gulping large quantities of water to filter. Baleen whales are not known to echolocate but produce a variety of sounds used for communication. Echoes from baleen whale vocalizations may help in navigating under ice or detecting the ocean floor.

thin-walled sensory organ found in the exoskeleton on each leg of semi-terrestrial ocypodid crabs.

a membrane in the cochlea of the ear that vibrates in response to sound. As sound vibrations progress down the ear, a fluid wave that is created by the movement of the third ossicle, the stapes, moves the basilar membrane. The basilar membrane is the part of the cochlea that separates sounds according to their frequency.

Cetorhinus maximus

charting of the sea floor using water depth measurements

an instrument that makes a record of the temperature at various depths in the ocean

an acoustic signaling device that continually sends out a repetitive signal. Acoustic beacons, sometimes called pingers, are used to mark the locations of underwater objects.

a graphical or other description of the response of a transducer used for sound transmission or reception as a function of the direction of the transmitted or incident sound waves.

a signal processing technique for the directional transmission or directional reception of a signal.

Erignathus barbatus

measurement of direction; the angle, with respect to magnetic north, to where the target is located

the hard, solid rock beneath surface materials such as soil as well as sand and other sediments on the ocean floor.

a unit used in the comparison of power levels or of intensities of sounds corresponding to an intensity ratio of 10:1.

Delphinapterus leucas

living on the bottom of the sea (or a lake).

a contraction of “biological diversity,” it generally refers to the amount of variability within species, among species, and among ecosystems.

an action or activity that affects an animal's ability to grow, survive, or reproduce.

measure of the amount of living material in an area, usually expressed in units of weight per unit volume

an aquatic mollusk that has a compressed body enclosed within a hinged shell, such as oysters, clams, mussels, and scallops.

Pogonias cromis

Sebastes melanops

 Rissa tridactyla

Mesoplodon densirostris

Sebastes mystinus

Prionace glauca

Balaenoptera musuculus

Micromesistius poutassou

Thunnus thynnus

Tursiops truncatus

Balaena mysticetus

a common activity of dolphins and other cetaceans in which marine mammals swim in front of a vessel, riding or surfing on the pressure wave created by the vessel

a sound signal that includes acoustic energy across a wide range of frequencies.

a feeding process where whales trap a school of prey (fish or krill) by blowing a series of bubbles as the whales swim to the surface. The bubbles form a curtain that rises to the surface of the water and concentrates the prey in the center. The whales charge through with their mouths open to engulf the fish or krill.

the frequency equal to the reciprocal of the time interval between the shock wave and the first bubble pulse.

secondary shock waves of explosions in which the bubbles repeatedly grow larger and smaller.

the anterior portion of the oral cavity, also sometimes referred to as the vestibule or entry area of the oral cavity. It is the region bounded by teeth and gums, jaws, and cheeks.

the upward force on a free floating or submerged object, independent of the object's weight; gives submerged objects the weightless appearance.

a rapid series of broadband clicks similar to those used in echolocation, but with a much shorter interclick interval of 0.5-10ms. Given this very high pulse repetition rate, greater than 300 pulses/second, more clicks are produced per unit time with burst-pulsed sounds.

the harvest of fish (or any marine organism) other than the species for which the fishing gear was set

string like substance that is secreted by mussels to allow the mussel to attach to hard substrates like rocks

a frequency weighting function that was originally designed to predict the human ear’s sensitivity to tones at high noise levels; however, nearly all noise measurements for hearing conservation are measured with A-weighting; units dB(C) or dBC.

depression formed at the summit of a volcano

Hemisquilla californiensis

Zalophus californianus

thick, white patches of hardened skin, called chitin, that are covered with tiny crustaceans, called whale lice." These patches are found on the heads

the sudden release and breaking away of a mass of ice from a glacier, iceberg, ice front, or ice shelf.

sharp, fang-like teeth adapted for capturing and penetrating prey

Arctocephalus pusillus

the smallest of the network of blood vessels throughout an organism

A hard, protective, shell-like outer covering found in crustaceans (e.g. crabs and lobsters) as well as turtles.

a heart-shaped curve generated by a point on a circle that rolls without slipping on another fixed circle of the same diameter.

Panulirus argus

fish that are born in saltwater, migrate into freshwater as juveniles where they grow into adults, before migrating back into the ocean to spawn.

The narrow part of the body to which the caudal fin (or tail) attaches to the body.

formation of gas-filled cavities in liquids in motion when the pressure is reduced to a critical value. Low pressure regions are often created by rotating ship propellers. As the propellers rotate, bubbles form in the water. A loud acoustic sound is created when these bubbles collapse.

the complex of nerve tissues that controls the activities of the body. In vertebrates it comprises the brain and spinal cord.

squid, cuttlefish, octopods, and nautilus.

order of mammals that includes whales, dolphins and porpoises

a material property of a medium, defined as the density of the medium times the sound speed through the medium.

the first two claws of a crab. A male fiddler crab has an enlarged claw or cheliped.

Oncorhynchus tshawytscha 

for Crustaceans, they are located at the joint segments and they serve as mechanoreceptors (sensory organs).

family (Cichlidae) of freshwater fishes found throughout tropical and subtropical waters of the Americas, Africa and parts of Asia

hair cells of the neuromast

the enclosing boundary (perimeter) of a curved geometric figure, especially a circle.

located around or found in one of Earth's polar regions

Periclimenes longicarpus

a short pulse of sound, often used to describe pulses produced by toothed whales for echolocation.

rapid sequence of clicks, produced by whales and dolphins, that are associated with echolocation. The clicks are emitted from the melon of the whale.

a scientist who studies climate

fish belonging to the herring family

fused or grown together

the spiral-shaped chamber within the inner ear that transforms sound waves into nerve impulses. The cochlea is a fluid-filled organ that houses many structures related to hearing, including the basilar membrane and the organ of Corti. It is considered the organ of hearing.

Gadus morhua

Cyprinus carpio carpio

Delphinus capensis (long-beaked common dolphin), Delphinus delphis (short-beaked common dolphin)

Balaenoptera acutorostrata

Octopus vulgaris

Palaemon serratus

the area over which one individual can detect the signal of another.

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear explosions on Earth whether for military or for peaceful purposes. It was adopted by the United NAtions General Assembly in 1996. The treaty contains provisions for monitoring which include acoustic monitoring. The treaty is not yet in force because it has not been ratified by some nations.

oceanographic tool used to determine the essential physical properties of sea water: conductivity (salinity), temperature, and depth. Depth measurements are derived from measurement of hydrostatic pressure and salinity is measured from electrical conductivity. The CTD may be incorporated into an array of sampling bottles referred to as a carousel" or ""rosette"". The sampling bottles close at predefined depths

animals (or plants) belonging to the same species

the gently sloping undersea region between a continent and the deep ocean.

a type of hormone produced by the adrenal glands. Corticosteroids levels may be elevated as a response to stress.

behaviors in animals, that are used to initiate mating

the arrival angle at which a sound wave traveling from one medium to another medium will be refracted along the interface of the two media. If a wave traveling from one medium to another medium with a higher speed of sound hits the interface between the two media at an arrival angle less than the critical angle, only reflection will occur; at an arrival angle above the critical angle, some of the sound will be reflected and some will be refracted into the faster medium.

specific geographic area(s) that contains features essential for the conservation of a threatened or endangered species and that may require special management and protection.

a class of mainly aquatic, gill-breathing arthropods such as crabs, lobsters, shrimp, and barnacles. They usually have a hard exoskeleton and two pairs of antennae.

gel-like cover of cilia in the neuromast

Ziphius cavirostris

Ziphius cavirostris

one complete vibration of a particle through a wave, e.g., from equilibrium to the crest through equilibrium to the trough and back to equilibrium.

energy spreading out from a sound source in the shape of a cylinder; no energy radiates above the top or below the bottom of the cylinder

a unit of relative pressure when the pressure of the sound wave is characterized as the peak pressure.

a unit of relative pressure when the pressure of the sound wave is characterized as the peak-to-peak pressure.

crustacean that has five pairs of walking legs, a segmented body, and chitinous exoskeleton. Examples include lobsters, crayfish, crabs, shrimps, and prawns.

a relative unit used to describe sound intensities. Written as dB. See Advanced Topic: Introduction to Decibels.

known as the bends, a condition that occurs in deep-sea divers caused by the formation of nitrogen bubbles in the blood and tissues following a sudden decrease in the surrounding pressure. This occurs when ascending rapidly from a deep dive and is characterized by severe pains in the joints and chest, skin irritation, cramps, and paralysis.

cetaceans of the family Delphinidae, the most diverse of cetacean families. Includes oceanic whales and dolphins, such as, killer whales, pilot whales, common dolphins and bottlenose dolphins

the distribution of a quantity (such as mass, electricity, or energy) per unit usually of space (such as length, area, or volume); the degree of compactness or concentration of a substance.

the removal and/or damage of netted or hooked fish and bait from fishing gear.

formed or developed from something else; not original. NOTE: different areas of science have more specialized definitions for this term (e.g. in paleontology, derived characteristics means something has evolved to fit a particular pressure).

the probability of correctly deciding on the basis of a statistical test that a signal is present when it is in fact present.

the signal-to-noise ratio (SNR) (in decibels) required to achieve a specified probability of detection p(D) for a given probability of false alarm p(FA) when deciding whether or not a signal is present at a receiver.

to explode

migrating between saltwater and freshwater to complete a life cycle.

vocalizations or calls of cetaceans that are characteristic of a particular group or pod

Directional Frequency Analysis and Recording device; passive acoustic sonobuoy

information that is represented in a coded form, as a series of zeros and ones

when an underwater sound (or some other stimulant) acts like a dinner bell, alerting and attracting an animal to the presence of a food source.

producing or receiving sound only from certain angles or directions

the linear distance in a given direction between a point and a reference position.

the frequency of occurrence of a specific value in a set of measurements.

of or during the day.

the raising or lowering of the frequency of a sound due to the motion of the source of the sound relative to the listener. The most common example is the rising frequency of a train whistle as the train approaches.

of or pertaining to the upper surface.

the main fin found on the back of fishes and some marine mammals. Some whales, such as the killer whale, have tall dorsal fins, while other whales (i.e. belugas and bowheads) have no dorsal fin.

a signal that decreases in frequency over time

to vibrate a muscle in, on, or near, the swim bladder that produces a loud, low-pitched grunt sound

internal passage involved in the flow of fluids through an organism

Dugong dugon

the length of a sound in seconds

marine invertebrates with tube feet and five-part radially symmetrical bodies. The group includes sea urchins, sea stars, sea cucumbers, brittle stars, and crinoids.

determining the distance to an object by measuring the time between transmitting a sound signal and hearing its echo.

a unique sonar return (reflection) that can be used to identify individual species of marine organisms, such as fish, or other submerged objects

when individual (sonar) targets are spaced far enough apart that they can be distinguished from one another, the number of targets are counted (and the number of fish estimated).

when more than one target (e.g. a fish school) is located in an acoustic beam at the same depth, and it is not possible to resolve them separately.  The total acoustic energy backscattered by the school or aggregation is integrated together, and this total is divided by the (previously determined) backscattering coefficient of a single animal, giving an estimate of the total number. Echo-integration assumes that the total acoustic energy scattered by a group of targets is the sum of the energy scattered by each individual target.    

a process for locating distant or hard-to-see objects using the reflection of sound waves. The distance of objects or depth of the seafloor can be determined by measuring the time it takes for reflected sound waves (echoes) to return to the sound source. Some whales and dolphins use echolocation to identify underwater objects and to help find food.

the technique of measuring the depth of a body of water by means of an echosounder, an electrical depth sounder that uses sound echoes. The instrument emits sound waves that travel to the bottom of the ocean and are reflected back. Depth is determined by timing how long it takes the sound pulse to leave the instrument, travel to the seafloor, and return to the receiver on the ship.

the process of calculating the probability of adverse ecological effects

the scientific study of the relationship between organisms and their environment.

ecologically distinct groups or communities; in this case, groups exhibiting different dietary specializations and corresponding behavioral adaptions, such as hunting techniques and acoustic repertoires.

energetic, swirling, unsteady flows that are found almost everywhere in the ocean

the source level of an array when considered as a single omnidirectional sound source

a group of cartilaginous fish that comprises the sharks, rays, and skates.

a group of fishes, including sharks, rays and skates, that has a skeleton made of cartilage rather than bone; they also do not have a swim bladder.

the electrical activity of neurons when stimulated (see auditory brainstem response (ABR)).

Mirounga

any species that is in danger of extinction

native to or prevalent in a particular area or region; not found in other places.

filled with sound.

whales, seals, sea lions, and other marine animals may come into contact with lost or active fishing gear, causing the gear to become twisted around their bodies and/or snagged on different body parts. When this occurs, the animal is considered entangled.

the surface location of an earthquake.

assumption that sounds of equal SELcum produce an equal risk for hearing loss (i.e., if the SELcum of two sources are similar, a sound from a lower level source with a longer exposure duration may have similar risks to a shorter duration exposure from a higher level source).

the assumption in hearing studies that sounds that are perceived to be equally loud result in equal response times, thereby allowing response time to be a proxy for perceived loudness.

a graph of the perceived intensity (loudness) of sounds. The loudness of a sound is different for different frequencies.

the rest position of the particles in a medium

those waters and substrate necessary for fish for spawning, feeding, or growth to maturity.

a coastal body of water formed when freshwater from rivers and streams flows into the ocean, mixing with the seawater. Estuaries and the lands surrounding them are places of transition from land to sea, and from freshwater to saltwater. Although influenced by the tides, estuaries are protected from the full force of ocean waves, winds, and storms by the reefs, barrier islands, or fingers of land, mud, or sand that surround them.

Perca fluviatilis

Dicentrarchus labrax

Palinurus elephas

a zone extending up to 200 nautical miles (370km) from a nation's territorial waters into the ocean where that nation has jurisdiction over natural resources such as fisheries and energy production. The Exclusive Economic Zone is defined in the United Nations Convention on the Law of the Sea. Also called the EEZ.

a hard outer structure, such as the carapace of a lobster or crab, that provides protection or support for an organism (especially invertebrates).

a probe which is dropped from a ship and measures the temperature as it falls through the water. Two very small wires transmit the temperature data to the ship where it is recorded for later analysis. The probe is designed to fall at a known rate, so that the depth of the probe can be inferred from the time since it was launched. By plotting temperature as a function of depth, the scientists can get a picture of the temperature profile of the water.

a device that uses explosive material to generate controlled acoustic energy.

still existing; not extinct.

the end of an organism or group of taxa. The moment of extinction is generally considered to be the death of the last individual of that species (although the capacity to reproduce and recover may have been lost before this point).

the movement of an entire population out of a region

to estimate or expand unknown data based on known facts and/or observations.

using evidence and inferences from a similar situation to project information about a related event or process. Extrapolation can also be used to apply or transfer experimental observations from a model to the real world.

incorrectly deciding on the basis of a statistical test that a signal is present when it is in fact absent. A false positive.

the probability of incorrectly deciding on the basis of a statistical test that a signal is present when it is in fact absent.

Pseudorca crassidens

an error when one concludes that there is not a real difference between two means when, in fact, there is a difference; also called a Type II error.

an error when one concludes that there is a real difference between two means when, in fact, there is not; also called a Type I error.

the sound field at a distance from a sound source array where the wave fronts created by the individual sound sources are in phase

a fat globule in the bloodstream that is often caused by physical trauma such as fracture of long bones, soft tissue traum, or burns.

Pimephales promelas

fruitful in offspring or vegetation

Balaenoptera physalus

teleost bony fishes, in other words, not sharks/skates/rays, and not shellfish.

Neophocaena phocaenoides

the industry or occupation devoted to the catching, processing, or selling of fish, shellfish, or other aquatic animals.

two or more fish species. For example, if you have three fish species in an aquarium (such as a clownfish, damselfish, and goby), you would say three fishes." If you have three clownfish (all of the same species)

the two lobes of a whale tail.

observations concentrated on individual animals that record everything they do

to search for food

the way in which an animal searches for food; the process, or series of actions, that an animal goes through to find food

Pontoporia blainvillei

the rate of repetition of a regular event. The number of cycles of a wave per second. Expressed in units of Hertz (Hz)

a graph of a sound that plots the intensity of each frequency in the sound. Plural is spectra.

a method for quantitatively compensating for the fact the animals do not hear equally well at all frequencies within their hearing range.

responding out of fear

a boundary between two water masses with differing properties such as temperature and salinity

the lowest frequency in a complex wave.

nerve cells that have their cell bodies outside of the central nervous system (the brain and spinal cord). Auditory ganglion cells carry sound information from the inner hair cells to the auditory nerve.s

a modification of the inner lining of the bladder, which works with the rete mirabile to force gases into the bladder

Carassius auratus auratus

Epinephelus itajara

Balistes capriscu

Eschrichitus robustus

Carcharodon carcharias

Chelonia mydas

a gas that traps heat in the atmosphere.

Halichoerus grypus

a measure of the cargo carrying capacity or the volume of a ship.

information, or the determination of facts, provided by direct observation.  Often performed to check the accuracy of data or other observations.

Gobio gobio

a hindrance or obstruction that restricts migratory movements and/or prevents a species from accessing habitat necessary for spawning, foraging, and other activities.

to become accustomed to something through repeated or prolonged exposure

Melanogrammus aeglefinus

mechano-transducers that detect energy or pressure changes. They are complex structures that include a cell body on the surface of a membrane. At the base of the hair cell are one or more neural synapses. On the upper surface of the hair cell are hair-like projections called stereocilia, commonly in bundles. These stereocila bend in response to a range of stimuli based on the species, some from fluid motion, some in association with crystals or otoliths, some because of being embedded in a second membrane. When these stereocila bend, they trigger a release of chemicals that initiates the electrical signal (neural impulse) that is carried to and processed by the brain.

Phocoena phocoena

Phoca vitulina

distortion of a pure tone associated with the presence of undesired harmonics at frequencies that are a multiple of the fundamental frequency of the signal.

the part of a signal whose frequency is an integer multiple of the fundamental frequency. Harmonic frequencies are related to each other by simple whole number ratios, for example if the fundamental frequency is f, the harmonics have frequencies of 2f, 3f, 4f, etc.

Monachus schauinslandi

an expedition to Heard Island in the southern Indian Ocean during which acoustic sources suspended below a ship transmitted acoustic signals to receivers around the globe. Heard Island was selected because signals transmitted from that location can reach both coasts of North America. HIFT showed that underwater acoustic signals could be received worldwide and serve as a method for measuring global ocean warming.

a fish species in which the swim bladder aids very little or not at all in hearing sensitivity

groups of marine mammals defined by the generalized range of frequencies that species in the group can hear.

the range of frequencies the ear of an animal can detect.

a fish species in which the swim bladder is directly connected to the inner ear and provides increased hearing sensitivity

very thick oil that has little to no evaporation and/or dissolution properties and weathers very slowly. Heavy oil is depleted in hydrogen relative to light oil, and fewer refined products are derived from heavy oil. Cleanup of heavy oils is also very difficult.  Heavy crude oil is an example of a heavy oil.

flow of blood from a ruptured blood vessels; excessive bleeding

an animal or plant having both male and female reproductive organs

the unit of frequency; the number of cycles, or wavelengths, in a second (cycles/second)

a system or organization in which people, animals, or groups are ranked one above the other according to status or authority.

the northernmost part of the Arctic, including the circumpolar Arctic Ocean with its surface ice and its most northerly coastal margins and islands.

a representation of a distribution by means of rectangles whose widths represent class intervals and whose areas are proportional to the corresponding frequencies of occurrence.

similar in position, structure, and evolutionary origin but not necessarily in function.

the main body of a ship or vessel (most of which goes under the water), including the bottom, sides, and deck but not the masts, superstructure, rigging, engines, and other fittings.

Megaptera novaeangliae

water ice with methane molecules trapped within the ice structure.

a large, industrial hammer that is operated by a fluid that is under pressure (hydraulics). A hydraulic hammer is a modern type of piling hammer used in place of diesel and air hammers for driving steel pipe, precast concrete, and timber piles.

acoustics in water

an organic compound containing only hydrogen and carbon; often occurring in crude oil, natural gas, and coal, as well as plant life.

of, relating to, or operated by the force of liquid in motion

a vessel that is lifted partially above the water by wing-like structures mounted on struts below the hull of a boat.

the conversion of kinetic energy produced by flowing water into electricity, or other forms of energy.

an underwater microphone that will listen to, or pick up, acoustic signals. A hydrophone converts acoustic energy into electrical energy and is used in passive underwater systems to listen only.

several hydrophones attached to each other at known fixed distances so the location of sound sources can be calculated.

The pressure at a point in a fluid at rest due to the weight of the fluid above it.

relating to hot water circulation in the ocean crust.

a hot spring on the seafloor

a condition where the body produces or absorbs more heat than it can dissipate, causing one's body temperature to become elevated to a potentially dangerous level.

a condition where the body loses heat faster than it can produce it, causing one's body temperature to become dangerously low.

a tentative explanation proposed by a scientist for observations that cannot be explained by existing scientific theories. A careful statement of a tentative or provisional conclusion to be tested.

a sheet of floating sea ice.

the underwater portion of an ice ridge.

Inverted Echosounder; an instrument used to measure the temperature of the water column at a single point

a bodily defense reaction that recognizes an invading substance (such as a virus, fungus, or bacteria, or a transplanted organ) and produces antibodies specific to that invading substance.

a broadband signal generated by sound sources such as explosions and airguns in which the sound pressure is very large at the instant of the explosion and then decays rapidly away; the duration of the peak pressure pulse is usually only a few milliseconds.

the wave moving towards the reflector

sound waves that have a frequency that is lower than what humans can hear (i.e. below about 20 hertz). Baleen whales, such as blue and fin whales, produce these low frequency sounds. The sounds may be used to communicate over long distances and to detect large-scale topography of the seafloor. On land, elephants also use these powerful infrasonic sounds to communicate over long distances.

the innermost part of the ear that is surrounded by the skull bone. It contains the organs of balance and hearing. The inner ear contains the vestibular system that helps maintain our balance. It also contains the cochlea that transforms sound waves into nerve impulses that are carried to the brain.

the average amount of sound power (sound energy per unit time) transmitted through a unit area in a specified direction. The unit of intensity is watts per square meter. For simplicity, the magnitude of the intensity is often referred to as the intensity, without specifying the direction in which the sound is traveling.

the time it takes an echolocation signal to be sent out and an echo to return, combined with the time the animal needs to receive and process that echo.

an animal that lacks a backbone (marine examples include lobsters, shrimp, squid, clams, crabs, and sea stars).

an atom or a group of atoms that has an electric charge. Positive ions, or cations, are formed by the loss of electrons; negative ions, or anions, are formed by the gain of electrons.

Sebastes atrovirens

technique used by dolphins to drive fish away from protected areas such as sea grass beds. A dolphin will lift its tail and lower body out of the water and crash it down on the water surface. This causes a loud splash and creates a trail of bubbles under the water. The bubbles startle the fish hiding in the seagrass and flush them from their hiding places, making it easier for the dolphin to detect them.

a species on which other species in an ecosystem largely depend, such that if it were removed, the ecosystem would drastically change

Orcinus orca

Evechinus chloroticus

the energy possessed by a system or object as a result of its motion.

a unit of speed equal to one nautical mile (1.852 km) per hour, approximately 1.151 mph.

small, shrimp-like invertebrates (also called euphausiids) that swarm in dense patches within the water column or at the sea surface. They have hard mouths and tail parts that reflect sound. Krill is an important food source for many marine organisms including whales and seals.

a complex system of interconnecting bony or membranous cavities, particularly those concerned with hearing and balance

Elops saurus

Acipenser fulvescens

the soft, downy hair that covers some newborn mammals; in Arctic seals, it is a white fur that is highly prized by seal hunters, most famously associated with the hunting of harp seal pups

an inflatable “pouch”, or often a pair of pouches, that are generally located ventral to the larynx in many mammals, particularly in primates (but not in humans), hooved mammals (e.g., reindeer, horses, antelopes), and cetaceans. The functions of laryngeal sacs are not completely understood. Like the vocal sacs of frogs, laryngeal sacs may amplify calls but in some species, they may assist extended, rapid vocalizations by acting as air reservoirs.

the upper part of the trachea (air passage) that contains the vocal folds

sensory organ, found in fishes, that runs long the length of their body. The lateral line allows fish to sense movement.

the angular distance of a place north or south of the earth's equator, or of a celestial object north or south of the celestial equator, usually expressed in degrees and minutes.

Hydrurga leptonyx

Triakis semifasciata

strong, flexible bands of tissue that hold two or more bones together at moveable joints. They help restrain the movement of bones at the joint.

very fluid oil that has a strong odor, high concentrations of soluble, toxic compounds, and a high evaporation rate. Light oils consist largely of benzene and toluene.  Gasoline and diesel fuel are examples of light oils.

Raja erinacea

determine the direction the sound is coming from.

Low Frequency and Ranging sonobuoy; a type of passive acoustic sonobuoy

of, relating to, or expressed in terms of logarithms. A logarithm is the power to which a base, such as 10, must be raised to produce a given number.

the unconscious tendency of a person or animal to raise and/or lower their voice when going from a relatively quiet to a noisy environment and vice versa

Diadema setosum

Loligo pealeii

a disturbance in which the particles and the energy move in the same direction

how loud a person perceives a sound to be. Not the same as the intensity of the sound. The perceived loudness varies with frequency.

a method of feeding underwater in which the predator moves forward with its mouth open, engulfing the prey along with the water surrounding it.

Halobatrachus didactylus

method of producing a three-dimensional image of object by recording the signals the object emits when placed in a magnetic field

Trichechus spp.

one of the jaw structures of animals. For example, in vertebrates, it is the lower jaw bone; in insects it is one of the anterior mouth parts.

the accumulation of microorganisms, plants, algae, and/or animals on surfaces immersed in the ocean.  Buildup on marine vessels poses a significant problem.

acoustic interference that reduces the ability to detect, recognize, or understand sounds of interest.

a stranding event where 2 or more animals, excluding mother-calf pairs, unless a third animal strands, strand together in time and place.

the average of a set of measurements defined to be the sum of all of the measurements divided by the number of measurements.

sensory organs that cause response to displacement, pressure and vibrations

the "middle" value in the list of numbers. To find the median, observations are arranged in order from smallest to largest value. If there is an odd number of observations, the median is the middle value. If there is an even number of observations, the median is the average of the two middle values.

substance or material that carries or transports the wave from its source to other locations. In the open ocean, the medium through which the wave travels is the ocean water.

lipid-filled sac in the forehead of whales that helps to focus sound

small (less than 4 inches long) fishes, shrimps, and squids that live in the middle of the water column and near islands

the process of transformation from an immature form to an adult form.

rate of movement of methane from one reservoir to another, between seafloor sediments and the water column.

underwater mountain chain where new ocean crust is created.

the air-filled cavity that lies between the outer ear and the inner ear. The middle ear contains the ossicles which conduct sound vibration from the eardrum to the inner ear.

movement of a group of animals from one location to another

Incorrectly deciding on the basis of a statistical test that a signal is absent when it is in fact present. A false negative.

to make (something) less severe or harmful.

to shed the outer covering, or shell, which is then replaced by a new shell that is produced by the organism

equipment (often consisting of anchors and chains) which holds an item (such as a boat or underwater instrument) stable and secure in one place

the suspension (postponement and/or delay) of a particular activity.

the form and structure of an organism or any of its parts

Uca rapax

using multiple hydrophone arrays or streamers to record the reflected and refracted sounds from an air gun array

a sonar system that emits sound waves in a fan shape toward the sea floor and can measure the ocean depth over a wide swath.

sea ice that has survived at least more than one melting season (i.e. one summer). Multiyear ice contains much less brine and more air pockets than first-year ice. Less brine means "stiffer" ice that is more difficult for icebreakers to navigate and clear.

these large cetaceans are usually more than 9.1 m (30 ft) long and can be found throughout the ocean. Instead of teeth, mysticetes have a series of horny plates called baleen. The baleen is made from the same materials as human hair and fingernails. The baleen plates hang from the gums of the upper jaw and are used to filter small bits of food from the water. Baleen whales have symmetrical skulls and have two (or paired) blowholes.

the air spaces that connect the throat region with the openings of the nose, known as the nares. It is also sometimes referred to as the nasal passages.

sounds made up of only a small range of frequencies

Monodon monoceros

grown, produced, or originating in a particular place or in the vicinity (of, relating to, or present at birth).

the sound field near a sound source array where complex constructive and destructive interference occurs among the wave fronts created by the individual sound sources

the examination and dissection of a body to determine the cause of death; autopsy

New Millennium Observatory Network; a project, which records and transmits daily temperature and pressure readings from Axial Volcano

an electrical and chemical signal sent along nerve fibers

small, sensory receptors of arranged hair cells located along the lateral line, which respond to motion between the fish and the surrounding water

Mytilus edilus

an unwanted sound or a sound that interferes with the perception of another signal, whether it be through recording or hearing.

sounds made without the use of vocal folds or other body parts whose primary function is moving air for sound production. These sounds are typically made by slapping a body part on the water or land surface, or by forcefully clapping body parts together. Non-vocal sounds may be used to communicate acoustically.

a line that is perpendicular (makes a 90 degree angle) to a surface

Eubalaena glacialis

Eubalaena japonica

Hyperoodon ampullatus

Mirounga angustirostris

Callorhinus ursinus

Hippocampus erectus

Pandalus borealis

Clupea harengus

correctly deciding on the basis of a statistical test that a signal is absent when it is in fact absent.

the hypothesis that there is not a real difference between the means of two data sets.

a reduction in the pH of the ocean over an extended period of time, caused primarily by uptake of carbon dioxide (CO2) from the atmosphere. When CO2 is absorbed by seawater, chemical reactions occur that reduce seawater pH, carbonate ion concentration, and saturation states of biologically important calcium carbonate minerals. These chemical reactions are termed "ocean acidification" or "OA" for short.

a networked array of sensor systems that measure the physical, chemical, geological and biological variables in the ocean and seafloor as well as the overlying atmosphere.

a characteristic of the ocean that changes

noise over a range of frequencies where the frequency in Hertz of the upper end of the range is twice the frequency of the lower end

comprised of the lateral line and inner ear of fish; provides fish with balance, hearing, and the ability to feel vibrations from a distance

group of mammals that includes the toothed cetaceans. This includes some whales (such as sperm whales, orca or killer whales, and beaked whales) as well as all dolphins and porpoises.

next generation or baby of a certain species

an organ for smelling

having no directional component; producing or receiving sounds from all directions

organisms that eat both animals and plants

a type of foraging in which an animal feeds on a wide variety of prey and is able to adapt to whatever food becomes available.

the mouth, which forms the first chamber of the digestive system. It includes the space surrounded by the lips, teeth, hard and soft palates, cheeks, and tongue. The oral cavity ends at border of the pharynx, which is approximately the line just anterior to the tonsils.

the sensory part of the inner ear that converts sound signals into nerve impulses. Located on the basilar membrane, it contains sensory cells that transform vibrations into neural code for sound processing by the brain. It contains many important cells including the inner and outer hair cells.

Astronotus ocellatus

a flow periodically changing direction.

three tiny bones - the incus (anvil), malleus (hammer), and stapes (stirrup) - that lie in the middle ear. The ossicles conduct sound across the middle ear to the inner ear by forming a bridge between the eardrum and the oval window.

fur seals and sea lions that have visible ear flaps. They have an elongated neck and long front flippers. Their hind flippers can be turned forward for walking on land.

small bones in the inner ear which provide balance, and, in fish, aid in hearing

causing damage to the ear or its nerve supply.

the outermost part of the ear that is external to the ear drum or tympanic membrane. It directs sound waves down the air-filled ear canal onto the eardrum.

Sepiotheutis lessoniana

a membrane-covered opening between the middle ear and the inner ear. The oval window is connected to the third ear ossicle (stapes) and passes sound vibrations to the inner ear.

The pressure in the shock wave from an explosion that exceeds the existing atmospheric or hydrostatic pressure in the medium through which the shock wave is propagating.

Opsanus tau

also known as the Indo-Pacific humpback dolphin; Sousa chinensis

a U.S. Naval facility off the island of Kauai, Hawaii, that is the world's largest instrumented, multi-dimensional testing and training missile range. It is the only range in the world where submarines, surface ships, aircraft, and space vehicles can operate and be tracked simultaneously. There are over 1,100 square miles of instrumented underwater range and over 42,000 square miles of controlled airspace. Additional bottom-mounted hydrophones are being installed at PMRF in early 2011, and similar to AUTEC and SCORE, a Marine Mammal Monitoring (M3R) system is being installed to monitor vocalizing animals.

Lagenorhynchus obliquidens

a large area of floating ice pieces that have been driven together by wind, currents, etc. to form a nearly continuous mass of ice

thin bone in the back of the lower jaw that helps transmit sound to the middle ear

being an equal distance apart everywhere, extending in the same direction, never meeting or intersecting

the change in position of a particle with respect to time; in acoustics, particle motion is vibratory motion in which the particles move back and forth around an equilibrium point.

observation method where an acoustic device is deployed in the ocean to capture sounds from the surrounding environment (the instrument does not produce any sounds). The sounds received by the instrument are identified and classified. PAM has become an important tool in observing cetaceans, especially deep-diving species.

listening to sound sources; sound is only received

the transition between oceanic and continental landmasses that is not a plate boundary and therefore experiences little to no volcanic or earthquake activity.

the range in pressure between zero and the greatest pressure of the signal.

the range in pressure between zero and the greatest pressure of the signal

the range in pressure between the most negative and the most positive pressure of the signal

the uppermost of the paired fins on a fish

forelimbs of whales and dolphins that are used for stability and steering. These appendanges are generally flattened and paddle-like. Humpback whales have very large pectoral flippers, reaching 5 m (15 ft) in length.

rays that are part of the fishes pectoral fins but are free from the actual fin skin. These rays aid in the movement of the fish.

the bony or cartilaginous arch that supports the forelimbs of a vertebrate

a process by which a scholarly work (such as a paper or a research proposal) is checked by a group of experts in the same field to make sure it meets the necessary standards before it is published or accepted

scientific papers that have been subjected to evaluation by highly qualified experts in the field, the reviewers are usually anonymous and check the papers for inconsistencies, invalid conclusions and editorial errors

of, relating to, or living or occurring in the open ocean.

organisms that swim or drift in the water; these organisms are distinct from those living on or in the bottom sediments.

to recognize, discern, or understand.

the time duration between any point on a wave and the same point on the next wave, e.g., from one wave crest to the next wave crest; the time for a particle to make one complete cycle at a given point

a permanent increase in the threshold of hearing (minimum intensity needed to hear a sound) at a specific frequency above a previously established reference level

being at right angles

a figure expressing the acidity or alkalinity of a solution on a logarithmic scale on which 7 is neutral, lower values are more acid, and higher values more alkaline (basic).

teeth located in the gill or throat region

the location of a point within a wave cycle of a repetitive waveform, measured as the fraction of a wave cycle and often expressed as an angle; one cycle is 360º or 2 π radians.

seals, such as harbor seals, that have no visible ear flap. They have a streamlined body with short front flippers. Their hind flippers are directed backward and they are not used for walking on land.

a unit of loudness for pure tones that accounts for the perceived loudness of tones; the number of phon of a sound is the decibel of a sound at 1 kHz that is perceived to be just as loud.

light producing organs that appear as bright spots on various marine animals, including fishes and cephalopods.

a reaction to a change that requires a physical, mental or emotional adjustment or response.

the ability of some materials (notably crystals and certain ceramics) to generate electricity in response to applied mechanical stress

a material that produces electrical charges when subjected to pressure changes

Globicephala spp.

to query (another computer on a network, or in this case, an acoustic transponder) to determine the location of it.

Pagrus auratus

Pagrus auratus

the ear flap or outer part of the ear that extends from the head. The pinna funnels sound down the outer ear canal to the eardrum.

group of mammals that includes seals, sea lions and walruses

a ship pitch motion is an up or down, front to back motion.

Porichthys notatus

a wave in which the wave fronts are a series of parallel planes.

relatively small organisms that drift or float passively in the water and are carried wherever currents and tides take them. Plankton are often microscopic and are an important food source for other aquatic organisms. There are two types of plankton- phytoplankton (plants and autotrophs) and zooplankton (animals).

part of the spiny lobster that is found underneath the files. It is a soft piece of tissue that is found at the base of the antennae. The plecta is what the lobster pulls over the files to produce sound

containing or operated by air or gas under pressure.

a social group of whales that are clustered together. Some toothed whales, such as orcas travel in large, sometimes stable pods. They may group together to hunt their prey and/or migrate.

Ursus maritimus

Pollachius pollachius

small marine invertebrates that have hard, cup-like, limestone skeletons. Polyps live in large colonies where they take-in the calcium from the ocean and to build a hard shell around themselves. The skeletons grow one on top of one another and as a result a coral reef is able to grow.

the entire collection of individuals or items from which samples are drawn.

the probability of rejecting the null hypothesis in a statistical test when it is false.

the degree to which repeated measurements under unchanged conditions show the same results; reproducibility; repeatability.

adapted for seizing, grasping, or holding, especially by wrapping around an object.

the amount of force per unit area measured in units of atmospheres (atm)

a ridge produced on floating ice by buckling or crushing under lateral pressure of wind or waves (tide).

the change of an oceanographic variable with water depth

an instrument that sends out sound waves; consists of a transmitter and a transducer

a collection of individual projectors used together to generate a directional sound beam

the movement of sound through a medium.

a short duration broadband signal.

a sound that consists of one single frequency

Scarus vetula

floating instruments designed to move with a current and track the current's movements

Oncorhynchus mykiss

gradually increasing the sound source level

the instantaneous, local reduction in density of a gas or other medium resulting from passage of a sound wave.

something that listens for or receives sound; it may or may not record the sound

a curve that plots the cumulative distribution functions of the false-alarm probability and the detection probability on the x-axis and y-axis, respectively, to select the optimal detection threshold.

hole, corner or niche. For example, a rock recess, a place surrounded by rocks where a fish can hide

when acoustic energy causes supersaturated gas to be pumped into an existing small bubble, making the bubble increase in size

Sciaenops ocellatus

Epinephelus morio

the wave moving away from the reflector

the deflection of the path of a sound wave by an object or by the boundary between two media

any boundary between two media that causes the reflection of a wave

the bending of a sound wave towards a region of slower sound speed.

suite of behaviors that an animal may use in different contexts; in this case, the number of call types that have been distinguished based on categorization of vocal behavior.

resistive force is a force whose direction is opposite to the velocity of the body, or of the sum of the other forces; may be referred to as "friction" or "drag".

when sounds of specific frequencies cause air- or fluid-filled organs to vibrate with amplitudes that are large compared to the amplitude of incoming soundwaves

something that fills with sound and acts as a natural amplifier

a tightly packed bundle of capillaries which works with the gas gland to force gases into the bladder

echo

Phoca hispida

a strong, narrow surface current that flows rapidly away from the shore, returning the water carried shoreward by waves.

calculation to predict the probability of a behavioral response based on several factors, including sound received levels

Grampus griseus

a ship roll motion in a side-to-side tilting motion.

the square root of the average of the square of the pressure of the sound signal over a given duration. Root-mean-square is often abbreviated rms

whales of the family Balaenopteridae which includes humpbacks, sei, minke, fin, blue and Bryde's whales. They have throat pleats or ventral grooves that expand when the whales gulp large amounts of water while feeding.

upper jaw of whales that is elongated and looks like a beak

Anoplopoma fimbria

Pollachius virens

the total amount of salt dissolved in seawater; the units most often used are parts per thousand (ppt) but practical salinity unit (psu) is now the accepted standard in oceanography. An average salinity value for seawater is 35 ppt (psu) or 35 parts of salt in 1000 parts of water.

a layer of salt in a domed structure that was formed beneath the Earth's surface by the movement of salt over long periods of time. Salt domes are often associated with oil and gas deposits.

a subset of the population.

the number of individuals or items in a subset or sample of the population from which estimates of various statistical measures of the whole population are calculated.

Uca pugilator

small, silvery, slender fish of the herring family that have one short dorsal fin and no scales on their heads

a type of brown algae (of the genus Sargassum) that have a branching thallus (body) with lateral outgrowths differentiated as leafy segments, air bladders, or spore-bearing structures

satellite radar altimeters measure the ocean surface height (sea level) by measuring the time it takes a radar pulse to make a round-trip from the satellite to the sea surface and back. Features on the sea floor such as mountains add extra pull to Earth's gravity field, drawing more water around them and bulging the sea surface outward. The sea surface height can then be used to estimate ocean bathymetry. In 2014 satellite based bathymetry could resolve features of approximately 1.5 km (0.93 miles) or larger.

the diffusion of the sonar signal in many directions through refraction, diffraction and reflection, primarily due to the material properties of the seafloor. Scattering is one of the causes of attenuation in sonar, resulting in signal weakening.

a particle in seawater or the roughness on the sea surface or seafloor that causes sound energy to be scattered

when the path of a sound wave is broken up by objects (volume scattering) or the sea floor or sea surface (boundary scattering)

a large group of marine animals, for example fish, that swim together. The appearance of a large number of individuals may ward off potential predators.

family of fishes that contains approximately 270 species distributed in the Atlantic, Pacific, and Indian Oceans. This family is commonly known as the drums, which are renowned for their sound producing ability.

the orderly process by which scientists ask questions about the natural world and test their observations

to sink (a vessel) deliberately.

Enhydra lutris

condition of the surface of the ocean, measured on a scale 0-9, categorized by wave height.

Balaenoptera borealis

relates to an earthquake, earth vibration or volcano

a technique for examining the layers of the seafloor that uses the sound energy that is reflected by different layers in the seafloor.

a technique for examining the layers of the seafloor that uses the sound energy that is refracted by different layers in the seafloor.

a wave of energy caused by the sudden movement of rock, as in an earthquake, or by an explosion. Seismic waves travel trough the Earth and are recorded by a seismometer.

an instrument that records ground movement; used to detect and measure earthquakes

living mostly on land but requiring water and/or a moist environment (esp. as a breeding site). Most amphibians (e.g. frogs) and many crustaceans (e.g. crabs) are semi-terrestrial.

hearing loss due to damage to the nerves or inner ear structures

bundles of hair like projections (cilia) located on the surface of the inner ear that become stimulated by movement of the otolith against them. Stimulation of the hair cells results in sending a signal to the brain which is interpreted as sound.

a stiff hair, bristle, or bristle like part on an organism.

distinct difference in size or appearance between male and female sexes of an animal

a region of low sound intensity that sound waves traveling away from a source in the ocean do not reach, usually because the sound waves are refracted away from that region

ocean habitat on the edge of the continental shelf

a large school of fish

a fully developed compression wave of large amplitude, across which density, pressure, and particle velocity change drastically.

sonar is an acronym for sound navigation and ranging equipment. Sonar systems use sound waves to detect underwater objects by listening to the returning echoes. Side scan sonar uses the strength of the returning echo, not the travel time, to map the seafloor and identify objects on the seafloor.

sound that is used for a specific task, such as to convey information.

the amount (in decibels) by which the signal- to-noise ratio (SNR) exceeds the detection threshold (DT).

analyzing sounds from a receiver to detect and classify sound sources

the ratio that compares the received level of a sound signal and the background noise level. For example, it is easy to hear conversations in a quiet room, where the signal-to-noise ratio is high, but it is difficult to hear conversations at a noisy party, where the signal-to-noise ratio is low.

a unique sound that is associated with a specific sound source

tonal sounds produced by whales and dolphins that are unique to a particular individual and distinct from any other member of the group. Signature whistles provide a way to recognize individuals and help maintain group cohesion.

Bairdiella chrysoura

group of mammals that includes manatees and dugongs

a young salmon (or trout) at the stage of development when it assumes the silvery color of the adult and is ready to migrate to the sea.

Alpheus heterochaelis

SOFAR stands for SOund Fixing And Ranging. The sound speed minimum at 800-1000 meters of water depth is called the deep sound channel or, more historically, the SOFAR channel.

an acronym for SOund Navigation And Ranging equipment. Sonar systems use sound waves to detect underwater objects by listening to the returning echoes. The distance to the object or the seafloor can be calculated by measuring the time between when the signal is sent out and when the reflected sound, or echo, is received.

a muscle that is attached to the swim bladder. Rapid flexure of the sonic muscle against the swim bladder produces drum-like sounds commonly associated with courtship and spawning behavior.

a combined mechanism used by fishes to produce sound. The swim bladder is a gas filled organ primarily used for buoyancy control and is also important for hearing in some fishes. The sonic muscle is attached to the swim bladder. Rapid flexure of the sonic muscle against the swim bladder produces drum-like sounds commonly associated with courtship and spawning behavior.

sound producing

instrument that is dropped into the ocean (from either an aircraft or ship) to record underwater sounds. It includes a hydrophone and a radio transmitter to send sound signals back to the aircraft or ship. The U.S. Navy uses this instrument to listen for enemy submarines. Sonobuoys may also be used to record marine mammal calls and listen for earthquake activity.

graphic presentation of a sound. A sonogram plots the frequency vs. time and represents the different intensity of the frequencies with different colors. It is similar to a contour map or bathymetric map where the different colors represent different water depths. Also called a spectrogram

the production of light as a result of the passing of sound waves through a liquid medium. The sound waves cause the formation of bubbles that emit bright flashes of light when they collapse.

an area of slow sound speed that causes sound waves to become focused at this water depth

depth of the minimum sound speed within the sound channel. Sound waves cycle above and below the axis as they move through the sound channel.

the decibel level of the time integral (summation) of the squared pressure over the duration of a sound event; units of dB re 1 µPa2/s

the level of sound at different distances and depths from the source

10 times the logarithm of the ratio of the intensity of a sound wave to a reference intensity; also known as intensity.

10 times the logarithm of the ratio of the mean-square pressure of a sound to the square of a reference sound pressure. Sound pressure level will usually be shortened to sound level on the DOSITS website. Sound pressure level is given in relative units named decibels (dB). Sound pressures for transient signals are sometimes given as peak or peak-to-peak pressures, rather than mean-square pressure. To avoid ambiguity, the units for sound pressure level can be written dB rms for dB root-mean-square.

something that receives sound; sound receiver

something that creates sound

the decrease in intensity that occurs when a sound wave expands as it moves away from a source

a network of hydrophones mounted on the seafloors of the North Atlantic and North Pacific oceans maintained by the US Navy

acoustic environment as perceived or experienced and/or understood by a listener.  Soundscape is sometimes used synonymously with acoustic environment to refer to the composite of all sounds in an environment.

multiple sound sources combined to operate together for a specific purpose

the amount of sound radiated by a sound source. It is defined as the intensity of the radiated sound at a distance of 1 meter from the source, where intensity is the amount of sound power transmitted through a unit area in a specified direction. Source level is given as a relative intensity in units named decibels (dB). In underwater sound, decibels are referenced to a pressure of 1 microPascal (µPa). Therefore, source level is reported in units of dB re 1 µPa @ 1 m.

a state-of-the-art facility that provides training and testing services to the U.S. Navy’s Pacific Fleet. The underwater tracking range is located west of San Clemente Island, CA, and consists of 84 bottom-mounted hydrophones that provide a coverage area of approximately 660 square nautical miles. Similar to AUTEC, a Marine Mammal Monitoring (M3R) system has been established at SCORE to monitor vocalizing animals via the bottom-mounted range hydrophones.

Eubalaena australis

a sound source that uses an electric spark to generate a broadband signal.

the minimum difference or distance between two measured or computed values or objects that can be distinguished. It defines the limit of accuracy for a technique.

having a narrow base and a broad body (spade-shaped).

to produce, release, or deposit eggs for reproduction

a graphic presentation of a sound. A spectrogram plots the frequency vs. time and represents the different intensity of the frequencies with different colors. It is similar to a contour map or bathymetric map where the different colors represent different water depths. Also called a sonogram

Physeter macrocephalus

an elongated connective tissue sac in the forehead of the sperm whale that contains a waxy fluid called spermaceti

energy spreading out from a sound source in the shape of a sphere; the power is radiated equally in all directions from the sound source

Stenella longirostris

Palinurus elephas

Sprattus sprattus

a decrease in the intensity of a wave as it spreads out from a source

a common whale activity in which they lift their heads above the surface of the water and observe what is happening on the surface. Whales will often spin around in order to observe in all directions.

mollusks of the family Cephalopoda that are a favorite food of the sperm whale

an estimate of the variability of a set of measurements about the mean value; it is calculated by computing the square root of the variance.

an estimate of the variability of the mean value computed from a specific set of measurements; it is calculated by dividing the standard deviation of the measurements by the square root of the number of measurements; also often called the standard error of the mean.

a largely involuntary, defensive response to a sudden and/or threatening stimuli, such as a flash of light, a sudden  movement, or loud noise.  In fishes, this behavior is often displayed as a sudden bending of the body, and is a characteristic escape response.    

when particles move from a region of higher concentration to a region of lower concentration

findings of an experiment or study that have a low probability of being due to chance alone

mathematical analysis that is used to explain and compare numerical data. This analysis helps make broader generalizations about a population from a smaller number of specific observations.

a sac-like structure containing a mineralized mass (statolith) in association with numerous sensory cells.

a break or irregular change in frequency of a whistle.

short for stereophonic: a sound-reproduction system that uses two or more separate channels to give a more natural distribution of sound.

long, flexible hair-like structures that occur as a brush border on the surface of some membranes

groups of hair-like projections on the upper surface of a hair cell. When stereocila bend, they trigger a release of chemicals that initiates the electrical signal (neural impulse) that is carried to and processed by the brain.

fixed or settled in form.

the conducting, supervising, or managing of something, especially, the careful and responsible management of something entrusted to one's care.

an event where an aquatic animal, especially a marine mammal, lands on a beach or becomes stuck in shallow water, is dead or sometimes alive, and probably in distress.

Trigloporus lastoviza

a long (2000-6000 m) string of hydrophones typically used with air-gun arrays

the natural coping mechanism that allows the body to deal with stressful events. A group of physiological and behavioral processes enable an animal to adapt to changes in their environment.

anything that causes the body to respond by releasing stress hormones.

to produce a sound by rubbing two body parts together. Some fish make a shrill creaking noise by rubbing together bodily structures, especially skeletal parts.

Stenella coeruleoalba

Morone saxatilis

relating to the region immediately south of the Arctic Circle.

places where two tectonic plates move toward each other, and one plate plunges beneath the other plate. Often ocean crust is subducting beneath continental crust

underwater

narrow, steep-sided valleys on the seafloor.

a frequency that is below the audible range

the surface or medium on which an organism lives or grows.

the surface that an organism grows on or is attached to

more highly concentrated than is normally possible under given conditions of temperature and pressure

The zone within which waves approaching the coastline start breaking; also called the breaker zone.

a passive sonar system used to listen for noises produced by submarines. The system consists of a long string of underwater hydrophones that are towed behind a ship and pick up sounds in the ocean.

an explosive sound source used by the U.S. Navy that consists of 0.82-kg (1.8-lb) of TNT explosive material.

an area shaped like a broad strip.

a gas filled organ that is primarily used for buoyancy control but is also important for hearing in some fishes.

an expandable, gas-filled sac that helps fish maintain buoyancy in the water. This organ is also important for hearing in some species of fish.

having an interdependent relationship that benefits both parties involved.

a junction between a nerve cell and another nerve cell or a nerve fiber or a sensory receptor

a statistic that compares the sample means with the standard deviations of the sample means to determine whether the two sample means are statistically different.

the amount of sound reflected back toward a sonar by a target.

relating to the deformation of the earth's crust

a membrane that covers the surface of the organ of Corti in the cochlea of the inner ear

measuring and transmitting data from a remote location

a measure of the atomic and molecular vibration in a substance, in degrees. The response of a solid, liquid, or gas to the input or removal of heat energy.

a temporary increase in the threshold of hearing (minimum intensity needed to hear a sound) at a specific frequency that returns to its pre-exposure level over time

something that lives on land as opposed to in the water. Some animals, such as sea lions spend time both on land and in the water, they are considered to be both terrestrial and marine.

behavior in which an organism, for example a fish, defends its home

seismic energy that has been converted into acoustic energy in the ocean. Also a T-wave.

the outer skeleton of a sea urchin. It is made up of plates that encircle the sea urchin. Spines of the sea urchin grow from the test.

a broad-bladed seagrass occurring in shallow tropical and subtropical estuaries and nearshore marine waters

a hypothesis or group of hypotheses that have been consistently validated through scientific observations or experiments. Geology's theory of plate tectonics is an example of a well-documented and widely accepted theory.

a layer of water in an ocean or certain lakes, that separates warmer surface water from colder deep water. Temperature rapidly changes with depth in this region of the water column.

the measurement of temperature

 Uria lomvia

any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range (as defined in the U.S. Endangered Species Act).

the minimum intensity where a person with normal hearing can hear a sound. The intensity level varies with frequency. Lower frequency sounds generally have a much higher threshold of hearing. It ranges from 0 to 75 dB depending on the frequency.

the intensity level where sound is physically painful. Usually at 115-130 dB.

an increase (worsening) in the threshold of hearing for an ear at a specified frequency

Galeocerdo cuvier

trinitrotoluene; a chemical compound used as an explosive material.

opsanus tau

an instrument, such as a side scan sonar, that is towed behind a ship

a large membranous tube reinforced by rings of cartilage, extending from the larynx to the bronchial tubes and conveying air to and from the lungs; the windpipe.

the part of the sonar system that functions like an antenna, sending out sonar signals (sound waves) and receiving return echoes. The transducer converts electrical energy into sound waves and vice versa.

the decrease in acoustic intensity (due to spreading and/or attenuation) as an underwater sound wave propagates outwards from a source.

an instrument that sends out slectrical signals

a device for receiving an acoustic signal and automatically transmitting a unique return signal in response. Transponders are often used to show the location of something.

a disturbance in which the particles vibrate up-and-down and the energy moves left-and-right

a fluttering sound that alternates rapidly with another note

a tsunami is a series of ocean waves generated by sudden displacements in the sea floor, landslides, or volcanic activity. In the deep ocean, the tsunami wave may only be a few inches high at the sea surface. When a tsunami wave comes ashore it will increase in height and can become a fast moving wall of water several meters high.

a small rounded projection.

multiple airguns of different, carefully selected volumes that are fired at the same time.

a membrane that separates the outer ear from the middle ear. The eardrum vibrates in response to sound waves and passes the vibrations on to the bones of the middle ear.

an error when one concludes that there is a real difference between two means when, in fact, there is not; also called a false positive error.

an error when one concludes that there is not a real difference between two means when, in fact, there is a difference; also called a false negative error.

sound waves that have a frequency that is higher than what humans can hear (i.e. greater than 20,000 Hz). Bats and dolphins use these high frequency sounds for communication and navigation.

sound vibrations that have frequencies above the range of human hearing

the relative unit used to specify the intensity of an underwater sound. The phrase underwater dB is used on DOSITS to indicate decibels computed using root-mean-square (rms) pressure unless otherwise indicated. Underwater dB are referenced to a pressure of 1 microPascal (µPa), which is abbreviated as dB re 1 µPa. To be able to compare relative intensities given in dB to one another, a standard reference intensity or reference pressure must always be used. Scientists have agreed to use 1 microPascal (µPa) as the reference pressure for underwater sound. In air, however, scientists have agreed to use a higher reference pressure of 20 microPascals. It is important to remember that sound intensity given in underwater dB is not the same as sound intensity given in air dB. See the Advanced Topics Introduction to Decibels and Introduction to Signal Levels for additional information.

a signal that increases in frequency over time.

a space from which all gas and other matter has been removed

Phocoena sinus

an estimate of the variability of a set of measurements about the mean value; it is calculated by subtracting the mean from each of the measurements, squaring the differences, adding all of the squared differences together, and dividing by one less than the total number of measurements; the square root of the variance is the standard deviation.

a quantity, such as a velocity or force, that has both magnitude and direction.

the linear speed of an object in a specified direction.

of, pertaining to, or situated at the back or upper side.

having vertebrae or having a backbone or spinal column. Fish and humans are examples of vertebrates.

a pattern of movement that some marine organisms undertake each day. Usually organisms move to shallow waters at night and return to deeper waters during the day.

a fluid-filled maze of canals and chambers inside the inner ear that helps maintain orientation and balance.

a molecule's resistance to motion

relative frequencies of vital occurrences that affect changes in the size and composition of a population, such as birth rate or death rate

small bands of tissue within the larynx that vibrate (when air passes over them) to produce the sound.

connective tissue that strengthens the vocal folds via stiffness and support

the modification of an animal’s vocalization(s) based on acoustic signals in its environment, such as vocalizations by conspecifics.

sounds intentionally produced by animals that may be used for communication, navigation, and feeding. In humans, air is moved from the lungs and across the vocal folds (also known as vocal cords). The vibration of the vocal folds produce sounds that are formed into words and other vocal communication signals. We do not know how sound is produced by many species of marine mammals. The term vocalization is commonly used to refer to sounds that are produced by marine mammals; however, the use of the word vocalization does not imply that marine animals are using vocal folds to produce the sounds.

susceptible to being hurt or damaged.

the track of waves left by a ship or other solid object moving through the water.  It is caused by the flow of the fluid around the body.

Theragra chalcogramma

Odobenus rosmarus

disturbance caused by the movement of energy through a medium

a surface consisting of all points on a wave at the same position in a wave cycle.

a waveform presents the sound in a graph as positive and negative pressure on a relative scale (often from -1 to 1) through time. The relative pressure is related to the intensity of the sound.

a structure that guides waves by restricting the wave movement in one or more dimensions resulting in efficient transmission of the wave. For example, the SOFAR channel is a waveguide in the ocean.

the length of one cycle of a wave (one crest and one trough)

a series of bones which connect the swim bladder to the inner ear and carry vibrations between to the two, aiding in hearing.

Leptonychotes weddelli

narrow-band, tonal sounds produced by many toothed whales for communication purposes. Whistles are frequency-modulated, which means the pitch of the sound changes over time.

a heterogeneous mixture of sound waves extending over a wide frequency range (but equal intensities).

Lagenorhynchus albirostris

Lagenorhynchus spp.

Neophocaena phocaenoides

a ship yaw motion is rotation about a vertical axis through the ship or left to right turning of the ship.

Sebastes flavidus

microscopic animals, such as crustaceans and fish larvae, that drift in the water column.