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Hydrophone Handbook
12. Glossary of Terms
Term Definition Symbol Units Reference
Acoustic energy flow rate in the direction
of propagation per unit area normal to the
direction of propagation; the
instantaneous intensity typically varies due
to the oscillatory nature of acoustics so it is
common to refer to the temporal average
intensity, in which case the instantaneous
intensity is averaged over the repetition
period of the acoustic signal.
Acoustic Note – Instantaneous intensity is the I W/cm² www.electropedi
Intensity- product of instantaneous acoustic pressure a.com, 802-01-09
Instantaneous and instantaneous particle velocity. It is
difficult to measure intensity in the
ultrasound frequency range. For
or Average measurement purposes and if it is
reasonable to assume that the
instantaneous acoustic pressure and
instantaneous particle velocity are
substantially in phase along the beam(-
alignment) axis for a given frequency, than
the instantaneous intensity, I(t), is
approximated as p(t)2/ρc where p(t) is the
instantaneous acoustic pressure; ρ is the
density of the medium; c is the velocity of
sound in the medium.
Beam Area Area in a specified plane perpendicular to Ab cm² www.electropedi
Beam the beam axis, consisting of all points at --- a.com, 802-01-19
which the pulse-pressure-squared integral is
(Alignment) greater than a specified fraction of the --- www.electropedi
Axis maximum value of the pulse-pressure- a.com, 802-01-08
squared integral in that plane Note – Some
commonly specified levels are 0,25 and 0,01
for the −6 dB and −20 dB beam areas,
respectively.
Straight line that passes through the beam
centrepoints of two planes perpendicular
to the line which connects the point of
maximal pulse-pressure-squared integral
with the centre of the external transducer
aperture.
Beam Position determined by the 2D-centroid of --- --- www.electropedi
Centrepoint a set of pulse-pressure-squared integrals a.com, 802-01-07
measured over the –6 dB beam-area in a
specified plane.
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