  A new approach for for estimating the acoustic pressure in the near field of
a microphone based on non-intrusive direct measurement of acoustic particle
velocity is proposed. This method enables the estimation of the acoustic
pressure inside a domain located in front of the microphone membrane. The
acoustic pressure is calculated using the acoustic particle velocity on the
frontiers of this domain and a physical model based on the Green function of
the system. Results are obtained using the acoustic velocity measured with
Particle Image Velocimetry (PIV) in front of a microphone excited with a plane
wave inside a rectangular waveguide. They show that the diffraction of the
plane wave by the microphone leads to an increase of the acoustic pressure on
the microphone edge in the order of magnitude of 0.1 dB.
