CHARACTERIZATION OF FLUID MACHINES AS ACOUSTIC MULTI-PORT SOURCES

• Published in: Journal of sound and vibration 1996-10, Vol.197 (1), p.1-16
• Main Authors: Lavrentjev, J., Åbom, M.
• Format: Article
• Language: English
• Subjects: Acoustical measurements and instrumentation; Acoustics; Aeroacoustics and atmospheric sound; Aeroacoustics, atmospheric sound; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Physics
• ISSN: 0022-460X; 1095-8568
• DOI: 10.1006/jsvi.1996.0514

The aim of the work reported in this paper was to study the characterization of fluid machines (e.g., fans, pumps) as sources of fluid-borne sound in connected pipe or duct systems. Of special interest is the possibility of extending earlier published methods beyond the plane wave region: i.e., to include higher order modes effects. For machines which can be modelled as an acoustic multi-port source, a method which makes it possible to measure the source data is suggested together with a modal decomposition technique. In order to verify and test the measurement method and modal decomposition technique, measurements were first carried out on a small test-rig without flow, with an ordinary loudspeaker as a source. Then the method was tested on an axial fan mounted to the end of a duct. In both cases ten microphone positions, divided equally between two duct cross-sections, were used to separate the waves (five modes) into left- and right-going components. It was verified that the measured source data can be used to predict the sound field created by the fan at a given acoustic load.