AERNNOVAs activities performed in the work package related with cabin noise reduction inside FRIENDCOPTER project were focused on evaluation of damping performance of different APSCLDT (Active-Passive Segmented Constrained Layer Damping Treated) panels. Evaluation of noise and vibration reduction for different segmentations of APSCLDT panels were analyzed with commercial and own codes, correlated and tested in laboratory on special acoustic cavity. Different treated panels were tested in passive and active mode in order to compare noise reductions. Panels and acoustic cavity were acoustically excited by a speaker with white noise (band width 3.5 kHz) meanwhile the noise generated inside the cavity was measured with pressure microphone. Although no significant noise reductions were obtained, quite surprising results emerged from acoustic cavity tests. Obtained results clearly show that contribution of all structural panel resonances to overall noise in an enclosure have minor effect on overall interior cavity noise in comparison with acoustic resonance amplifications. Acoustic resonance amplifications are the main and most important noise carriers and contributors in enclosures. Panels have much more influence on excitation of acoustic resonances than on noise radiation. In other words helicopter panels are not so much noise radiators as they are exciters of acoustic resonances inside an enclosure like helicopter cabin.
Acoustic cavity with active- passive segmented constrained layer damping treated panels
2008
14 Seiten, 14 Bilder, 3 Tabellen, 3 Quellen
Conference paper
Storage medium
English
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