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Thursday, July 11 • 09:40 - 10:00
AIRCRAFT PANEL CURVATURE INTERACTION ON ACOUSTIC INSERTION AND TRANSMISSION LOSS PERFORMANCES

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Depending on aircraft size, curvature may induce strong modifications of acoustic radiation properties of the fuselage. The radiation efficiency of fuselage panels is naturally increased due to faster speed of sound of flexural waves below the shell ring frequency. This well-known effect leads to an increase of radiated power of curved panels, compared to flat design when both designs are submitted to the same vibratory ve-locity. The acoustic blanket performance is generally measured and predicted, assuming negligible curvature influence. The effective Sound Transmission Loss (STL) of the trimmed panel can then be predicted from STL measured (or predicted) in bare condition by adding to it the Insertion Loss (IL) of the acoustic blan-ket, measured (or predicted) in flat configuration. Transfer Matrix Method (TMM) applied to an assembly of flat infinite poroelastic/elastic layers is a practical tool to deliver the IL and is widely used in current en-gineering practice. This work analyzes curvature effect with a new TMM theory formulated in cylindrical coordinates and applied to infinite cylinders. This theory combined with SEA method predicts the full vi-broacoustic paths of the sound transmission in presence of curvature. The respective influence of the curva-ture of both blanket and bare panel radiation in sound transmission are then brought to the fore. Depending on blanket stiffness, differences of several dB in broadband frequency IL performance are observed, with and without curvature, well correlated with tests results and leading space for improving the engineering design of light-weighted insulators.

Moderators
ST

Stephan Tewes

Interior Noise Integration & Vibration, Airbus Operations GmbH

Authors

Thursday July 11, 2019 09:40 - 10:00 EDT
St-Laurent 6
  T03 Aero… aircrft noise & vibr., SS04 Aircr cabin noise & vibr cntrl