Glossary - T
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T

t-test
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.
target strength
the amount of sound reflected back toward a sonar by a target.
tectonic
relating to the deformation of the earth's crust
tectorial membrane
a membrane that covers the surface of the organ of Corti in the cochlea of the inner ear
telemetry
measuring and transmitting data from a remote location
temperature
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.
temporary threshold shift (TTS)
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
terrestrial
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.
territoriality/territorial
behavior in which an organism, for example a fish, defends its home
Tertiary wave
seismic energy that has been converted into acoustic energy in the ocean. Also known as a "T-wave".
test
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.
Thalassia
a broad-bladed seagrass occurring in shallow tropical and subtropical estuaries and nearshore marine waters
theory
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.
thermocline
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.
thermometry
the measurement of temperature
threshold of hearing
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.
threshold of pain
the intensity level where sound is physically painful. Usually at 115-130 dB.
threshold shift
an increase (worsening) in the threshold of hearing for an ear at a specified frequency
tiger shark
Galeocerdo cuvier
TNT
trinitrotoluene; a chemical compound used as an explosive material.
toadfish
opsanus tau
towfish
an instrument, such as a side scan sonar, that is towed behind a ship
trachea
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.
transducer
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.
transmission loss
the decrease in acoustic intensity (due to spreading and/or attenuation) as an underwater sound wave propagates outwards from a source.
transmitter
an instrument that sends out slectrical signals
transponder
an acoustic signaling device that automatically transmits a sonar signal upon reception of a designated incoming signal. Transponders are used to mark or track underwater objects.
transverse wave
a disturbance in which the particles vibrate up-and-down and the energy moves left-and-right
trill
a fluttering sound that alternates rapidly with another note
tsunami
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.
tubercle
a small rounded projection.
tuned airgun array
multiple airguns of different, carefully selected volumes that are fired at the same time.
tympanic membrane or eardrum
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.
Type I Error
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.
Type II 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.