Scanning a flue organ pipe with a p-v probe

In the course of the last 20 years, a major innovation in the field of acoustic instrumentation regard the development of acoustic velocity sensors based on MEMS technology, now p-v probes are commonly used for sound intensity measurements alongside the p-p ones. In order to arrange a stress test for p-v probes, we thought of measuring the inner sound field of a flue organ pipe starting from the results obtained by two of the authors with the p-p technique in 1997 [D. Stanzial, D. Bonsi, N. Prodi, Proc. of ISMA97, p. 353-358, Edinburgh, UK, 1997]. The measurements have been carried out along the axis of a square wooden pipe, over a wall of which, 44 holes, 4 cm apart from each other, were drilled and corked. In spite of the wind turbulence and high level of the internal sound, the direct measure of the acoustic particles velocity has been successfully carried out and then visualized. This paper reports the measuring techniques, the problems encountered and the obtained results. PACS no. 43.75.+a