Glossary - S
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.
sand fiddler crab
small, silvery, slender fish of the herring family that have one short dorsal fin and no scales on their heads
Sargassum or Gulfweed
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
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
condition of the surface of the ocean, measured on a scale 0-9, categorized by wave height.
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.
sensorineural hearing loss
hearing loss due to damage to the nerves or inner ear structures
sensory hair cells
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.
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.
side scan sonar
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
signal-to-noise (SNR) ratio
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.
group of mammals that includes manatees and dugongs
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.
sonic muscle - swim bladder
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.
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
sound channel axis
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.
sound exposure level (SEL)
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
sound intensity level
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
sound spreading loss
the decrease in intensity that occurs when a sound wave expands as it moves away from a source
Sound Surveillance System (SOSUS)
a network of hydrophones mounted on the seafloors of the North Atlantic and North Pacific oceans maintained by the US Navy
The composite of all sounds in an environment. The perception of the soundscape for each animal will vary depending on its hearing abilities.
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 commonly given as a relative intensity in units named decibels (dB).
Southern California Offshore Range (SCORE)
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.
southern right whale
A sound source that uses an electric spark to generate a broadband signal.
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
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
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.
standard deviation of the mean
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.
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.
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.
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.
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
narrow, steep-sided valleys on the sea floor.
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.
Surveillance Towed Array Sensor System (SURTASS)
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.
SUS (Signal, Underwater Sound)
an explosive sound source used by the U.S. Navy that consists of 0.82-kg (1.8-lb) of TNT explosive material.
a gas filled organ that is primarily used for buoyancy control but is also important for hearing in some fishes.
swim bladder (also called an air bladder)
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.
a junction between a nerve cell and another nerve cell or a nerve fiber or a sensory receptor