A - Scan		The maximum sound path that is displayed
Amplitude		Plan view
Angle Beam		Procedure using a pair of probes (pitch catch)
C - Scan		The spreading or bending of waves as they pass through an aperture or around the edge of a barrier
B - Scan presintation		The piezoelectric element in an ultrasonic search unit.
Back Reflection		The end of a reference block opposite of the entry surface
Back Surface		< 20,000 Hz
Beam Axis		The presence of a reflector
Beam Spread		Is perpendicular to the direction of the propagation
Critical Angle		The distance in the material from the surface of the test object to the depth at which a reflector can first be resolved
Crystal		Incident angle of the ultrasonic beam beyond which a specific refracted wave no longer exists.
Dead Zone		The response of the ultrasonic system display to the transmitter pulse (sometimes called main bang).
Diffraction		A measure of the smallest ultrasonic signal
Impeadance		Decrease in ultrasound intensity with distance
Initial Pulse		Acoustic center line of a search unit’s beam pattern ac defined by the locus of points of maximum sound pressure in the far field, and its extension into the near field
Far Field		Angle of incidence or refraction
Near Field		Electroacoustical device for converting electrical energy into acoustical energy
Longitudinal Wave		The ratio of the amplitude of an ultra sonic indication to the amplitude of the background noise
Resolution		Signal bouncing back from the far boundary of the part
Sensitivity		Presentation of Cross section view, Length, Reflectors and their relative position
Shear Wave		Selecting a segment of the time range for monitoring
Transducer		Base to peak height of a signal produced from A- Wave
Attenuation		Zone of the beam where equal reflectors give exponentially decreasing amplitudes with increasing dis- tance
Gate		Mathematical quantity used in computation of reflection characteristics at boundaries
Indication		Particle motion is perpendicular to the direction of propagation.
Pulse length		Horizontal base line that indicates distance
Range		Particle motion of the material is essentially in the same direction as the wave propagation.
Skip distance		Region of the ultrasonic beam adjacent to the transducer (Fresnel zone)
Straight beam		Divergence of the ultrasonic beam as the sound travels through a medium
Signal to wave ratio		A vibrating pulse Wave train
TOFD		A measure of the duration of a signal expressed in time or cycles
Transverse wave		Distance along the test surface
Ultrasonic		Separate indications from discontinuities having nearly the same range and lateral position