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Hydrophone Handbook

         Choosing a Hydrophone

 2.6 Directivity
 Directivity refers to the variation in sensitivity relative to the
 angle of incidence of the acoustic signal on the sensing element
 of the hydrophone. At a fixed frequency, smaller sensing areas
 are more omnidirectional and less affected by off-angle
 measurements.
 For instance, at 45° incidence the HGL-0085 (85 µm aperture)
 has a relative signal amplitude of 0.8 under a 5 MHz signal,
 compared with an HGL-1000 (1000 µm aperture) which has a
 relative amplitude of 0.05.

               HGL Hydrophone Directivity at 5 MHz

                           Transducer

                      -45          Pulsed Wave
                      Deg
                           0 Deg
  26
                                          +45
0NDA Corporation                          Deg

                           HGL
                                   Mount
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