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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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