Multi-reference, scan-based Nearfield Acoustical Holography (NAH) is a useful
measurement tool that can be applied when an insufficient number of microphones are available to
make measurements on a complete hologram surface simultaneously. The scan-based procedure can
be used to construct a complete hologram by joining together sub-holograms captured using a
relatively small, roving scan array and a fixed reference array. For the procedure to be successful, the
source levels must remain stationary for the time taken to record the complete hologram: that is
unlikely to be the case in practice, however. Usually, the reference signal levels measured during each
scan differ from each other with the result that spatial noise is added to the hologram. A
non-stationarity compensation procedure that is based on the acoustical transfer functions between
the sources and both the reference and scanning, field microphones are invariable is introduced.
Numerical and experimental results show well the availability of the introduced procedures to
suppress the spatially distributed noise and to get better sound fields partially separated.
A general radiation model for sound fields and nearfield acoustical holography in wedge propagation spaces
