Glossary - B
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B

backscatter
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.
Baiji
Lipotes vexillifer
baleen
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.
baleen whales
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.
Barth’s myochordotonal organs (Barth’s MCO)
thin-walled sensory organ found in the exoskeleton on each leg of semi-terrestrial ocypodid crabs.
basilar membrane
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.
basking shark
Cetorhinus maximus
bathymetry
charting of the sea floor using water depth measurements
Bathythermograph
an instrument that makes a record of the temperature at various depths in the ocean
beacon
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.
beam pattern
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.
beamforming
a general signal processing technique used to control the directionality of the reception or transmission of a signal on an array of sensors. Using beamforming during sound transmission, the majority of signal energy is transmitted in a specified direction. During sound reception, beamforming allows sensors to predominantly receive energy from a specified direction
bearded seal
Erignathus barbatus
bearing
measurement of direction; the angle, with respect to magnetic north, to where the target is located
bel
a unit used in the comparison of power levels or of intensities of sounds corresponding to an intensity ratio of 10:1.
beluga whale
Delphinapterus leucas
benthic
living on the bottom of the sea (or a lake).
biologically significant
an action or activity that affects an animal's ability to grow, survive, or reproduce.
biomass
measure of the amount of living material in an area, usually expressed in units of weight per unit volume
bivalve
an aquatic mollusk that has a compressed body enclosed within a hinged shell, such as oysters, clams, mussels, and scallops.
black drum
Pogonias cromis
black rockfish
Sebastes melanops
Blainville's beaked whale
Mesoplodon densirostris
blue rockfish
Sebastes mystinus
blue shark
Prionace glauca
blue whale
Balaenoptera musuculus
blue whiting
Micromesistius poutassou
blue-fin tuna
Thunnus thynnus
bottlenose dolphin
Tursiops truncatus
bowhead whale
Balaena mysticetus
bowriding
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
broadband
a sound signal that includes acoustic energy across a wide range of frequencies.
bubble feeding
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.
bubble frequency
the frequency equal to the reciprocal of the time interval between the shock wave and the first bubble pulse.
bubble pulses
secondary shock waves of explosions in which the bubbles repeatedly grow larger and smaller.
buccal cavity
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.
buoyancy
the upward force on a free floating or submerged object, independent of the object's weight; gives submerged objects the weightless appearance.
burst-pulse sounds
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.
bycatch
the harvest of fish (or any marine organism) other than the species for which the fishing gear was set
byssal threads
string like substance that is secreted by mussels to allow the mussel to attach to hard substrates like rocks