Experimental investigations on active suppression of sound propagation in a fluid-filled pipe

• Published in: The Journal of the Acoustical Society of America 1999-02, Vol.105 (2_Supplement), p.1090-1090
• Main Authors: Lippold, Roland, Scheuren, Joachim
• Format: Article
• Language: English
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.425110

The control of sound propagating along fluid-filled pipes is complicated because of the strong coupling between the structural and the fluid transmission path. If the propagation along the structural path is supressed (e.g., by passive compensation in the case presented), it is possible to reduce the propagating sound by active means only acting on the fluid. This statement was proved by several experiments. The experimental setup consisted of one pipe made of aluminum (length 4 m, wall thickness 5 mm, inner diameter 90 mm) and two pipes made of steel (3 m / 1.5 m, 2.5 mm, 70 mm) which were connected via 90-deg bends and filled with water. For excitation and compensation of sound in the fluid, shaker driven pistons acting perpendicular to the pipe axes were used. The frequency of the harmonic excitation in the frequency range from 600 up to 800 Hz was known to the compensation algorithm. If the passive compensation of the structural path was sufficient, the reductions of sound pressure in the fluid achieved at and behind the error sensor were between 10 and 20 dB. Otherwise, reductions of the same order were locally restricted to the position of the error sensor.