Glossary - D
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D

dB peak
a unit of relative pressure when the pressure of the sound wave is characterized as the peak pressure.
dB peak-peak
a unit of relative pressure when the pressure of the sound wave is characterized as the peak-to-peak pressure.
decibel
a relative unit used to describe sound intensities. Written as dB. See Advanced Topic: Introduction to Decibels.
decompression sickness
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.
delphinid
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
depredate
the removal and/or damage of netted or hooked fish and bait from fishing gear.
derived
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).
detection probability p(D)
the probability of correctly deciding on the basis of a statistical test that a signal is present when it is in fact present.
detection threshold
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.
detonation
to explode
dialect
vocalizations or calls of cetaceans that are characteristic of a particular group or pod
DIFAR
Directional Frequency Analysis and Recording device; passive acoustic sonobuoy
digital data
information that is represented in a coded form, as a series of zeros and ones
directional
producing or receiving sound only from certain angles or directions
displacement
the linear distance in a given direction between a point and a reference position.
distribution
the frequency of occurrence of a specific value in a set of measurements.
diurnal
of or during the day.
doppler effect
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.
dorsal
of or pertaining to the upper surface.
dorsal fin
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.
drumming
to vibrate a muscle in, on, or near, the swim bladder that produces a loud, low-pitched grunt sound
ducts
internal passage involved in the flow of fluids through an organism
Dugong
Dugong dugon
duration
the length of a sound in seconds