Study of establishment of measurement method of acoustic particle velocity and its applications to advanced investigation on acoustical phenomena

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Following studies were carried out to establish measurement methods on acoustic particle velocity. Then, application measurements were tried for the confirming of its usefulness to make unsolved acoustical phenomenon clear(A) Some calibration methods of the hot wire-type particle velocity sensor were tested for simultaneous measurement with sound pressure microphone. Relative correcting method by the transmission function value or by its approximation equation was effective.(B) Applications such as acoustic impedance measurements by use sound particle velocity sensor with microphone were performed. Some acoustic impedance measurements on the field with grass and on the snow-covered ground in the campus of Niigata University were carried out. Other acoustic impedance and sound propagation measurements also carried out on the very wide field with long grass in Hokkaido.(C) Calculations of the sound propagation characteristic based on the measured acoustic impedance values were tried, and … More these results were fairly corresponded to the measured results on the actual field.(D) Acoustic admittance measurements by the particle velocity sensor were applied to make clear for acoustical properties of perforated plate, the Helmholtz resonator and slit-type structure which are well known in architectural acoustics. Measured results clearly showed the resonant characteristics by sharp peak in each specific frequency.(E) The particle velocity sensor and its directivity were effective in the diagnosis for the soundness of porous drain pavement. It was very effective to realize compact potable inspective instruments.(F) The 3-D observation of sound propagation by particle velocity sensor in inserted porous absorber "glass wool" in light weight double wall was tried to investigate the bases of insertion effect of glass wool for the high sound insulation. Even in the case of grazing incidence to the wall, the propagation direction in the glass wool certainly changes to close to normal direction, then it weakened coincident effect. Less