COBEM99

S20 Vibroacústica

Title:

THEORETICAL AND EXPERIMENTAL ACOUSTIC MODAL ANALYSIS OF REACTIVE FILTERS IN PIPING SYSTEM

Summary :

REACTIVE FILTERS IN PIPING SYSTEM ARE A CONNECTION OF EXPANSION CHAMBERS AND PIPES. THE PRINCIPAL FEATURE IS THAT THE COMBINATION OF SUDDEN CHANGES OF THESE ELEMENTS CAN ACT AS A FILTER WHICH CAN BE APPLIED TO REDUCE NOISE AT LOW FREQUENCIES. THE REDUCTION OF THE NOISE WILL DEPEND ON THE EIGENVALUES OF THE SYSTEM. IN THIS PAPER THE THEORETICAL AND EXPERIMENTAL MODAL ANALYSES OF SUCH REACTIVE FILTERS IS INVESTIGATED. AN ACOUSTICAL SYSTEM COMPOSED OF 2 CHAMBERS AND 3 PIPES CONNECTED IN SERIES IS USED AS AN EXAMPLE. BOTH A LUMPED ACOUSTICAL MODEL AND A FINITE ELEMENT MODEL ARE USED. THE THEORETICAL PREDICTIONS ARE COMPARED WITH EXPERIMENTAL RESULTS OBTAINED USING A MODAL PARAMETER EXTRACTION METHOD THAT USES THE MEASURED FREQUENCY RESPONSE FUNCTIONS OF THE ACOUSTIC SYSTEM. WHILE, IN THE CASE OF MECHANICAL SYSTEMS, ANALYTICAL AND EXPERIMENTAL MODAL ANALYSES ARE WIDELY USED, FOR ACOUSTICAL SYSTEMS THIS IS CERTAINLY NOT TRUE. THE MAIN PURPOSE OF THE PAPER IS TO SHOW THE SIMILARITIES BETWEEN ACOUSTIC AND MECHANICAL EXPERIMENTAL MODAL ANALYSES. KEY WORDS: ACOUSTIC MODAL ANALYSIS, REACTIVE FILTERS, PIPING SYSTEMS, MODAL ANALYSIS.

Author :

Arruda, José Roberto de França
Huallpa, Belisario Nina

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