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Calibration
may not be accurately modeled as purely capacitive at higher
frequencies; in such cases, customers are advised to consider
purchasing a separate calibration which includes the use of
their extension cables.
8.7 Other Common Calibration Units
ML(f) is in units of voltage divided by pressure and is typically
expressed in V/Pa.
Alternatively, it can be expressed in units of dB re 1V/µPa using
the following equation:
1 = 20 × − 120
It is also common to express the calibration in terms of
acoustic intensity. Strictly speaking, a simple calibration factor
exists only under conditions of a sinusoidal signal and under
the assumption that intensity is equal to the time-averaged
value of the pressure squared divided by the acoustic
impedance of the medium. Under these conditions the
following relation applies:
=
where I is the acoustic intensity, and VRMS is the root-mean-
square voltage of the sinusoidal signal. The calibration factor K
is given by:
acousticim=pedance
where za is the of 2 medium (1.5 MRayls
the
for water). Because it is common to express I in units of W/cm2,
22 = 1.5 × 1010 2
for water.
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0NDA Corporation
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