APPLICATION OF DAMPED HELMHOLTZ RESONATORS AND DISTRIBUTED VIBRATION ABSORBERS FOR THE CONTROL OF NOISE TRANSMISSION INTO A CYLINDER

摘要

Control of noise levels transmitted into large cylindrical structures is important in manyrnaerospace applications. The paper presents the experimental results of applyingrndistributed vibration absorbers (DVAs), and optimally damped Helmholtz resonatorsrn(HR) for control of the low frequency interior noise of a sandwich composite cylinder.rnThe acoustic excitation was provided by a large loudspeaker array driven by a high-levelrnband passed white noise. The cylinder wall vibrations and interior acoustic levels werernmeasured at a large number of locations. The cylinder was treated with a set of 45 smallrnHelmholtz resonators, and 45 DVAs. Both the DVAs and HRs were tuned to targetrnspecific low frequency modes. A series of tests was performed with the bare cylinder,rnpassive acoustic foam, and the DVAs/HR treatment. It is shown that the peaks in therninterior sound pressure levels have been reduced by up to 15 dB for targeted frequenciesrnin the range 50 to 200 Hz.