Particle Velocity-based Statistically Optimised Near field Acoustic Holography.- Master of Science in Engineering Acoustics- by

By definition, Near field Acoustic Holography, nah, is a method used to estimate the sound field near a sound source. The Statistically Optimised Near field Acoustic Holography, sonah, is a variant of the conventional nah method. The fourier transform is avoided in sonah because the predictions of particle velocity and sound pressure are done directly in the time domain and thus some limitations and errors stay away. The estimation is done by measuring the particle velocity and the sound pressure in a plane close to the source, to reconstruct the sound field of the sound source. A device measuring particle velocity is now available on the market. The use of such a device was not possible in the past because there were no calibration method available. Calibration methods have been investigated, in Ref. [12] for instance. In this way, the particle velocity can be measured directly and used in sonah. In conventional near field acoustic holography, the direct measurement of this parameter has been investigated. The results are more accurate and less sensitive to transducer mismatch errors than the data only based on the measurement of sound pressure. First the idea was to examine whether there are similar advantages wit