Sound Transmission Through a Curved Honeycomb Composite Panel

Abstract

Composite structures are often used in aircraft because of the advantages offered by a high strength to weight ratio. However, the acoustical properties of these light and stiff structures can often be less than desirable resulting in high aircraft interior noise levels. In this paper, measurements and predictions of the transmission loss of a curved honeycomb composite panel are presented. The transmission loss predictions are validated by comparisons to measurements. An assessment of the behavior of the panel is made from the dispersion characteristics of transverse waves propagating in the panel. The speed of transverse waves propagating in the panel is found to be sonic or supersonic over the frequency range from 100 to 5000 Hz. The acoustical benefit of reducing the wave speed for transverse vibration is demonstrated. IntroductionPanels constructed from face sheets laminated to a honeycomb core are being incorporated into the design of modern aircraft fuselage and trim treatments. The mechanical properties of these panels offer a distinct advantage in weight over other commonly used construction materials.* The strength to weight ratio of honeycomb composite panels is high in comparison to rib stiffened aluminum panels used in previous generations of aircraft. However, the high stiffness and low weight can result in supersonic wave propagation at relatively low frequencies, which adversely affects the acoustical performance at these frequencies. †Poor acoustical performance of these types of structures can increase the cabin noise levels to which the passengers and crew are exposed.

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“…A formal way to describe an ADF consists on superimposing an infinite number of uncorrelated plane waves through different directions. In a FEM model, a finite number of uncorrelated plane waves can be generated and the pressure due the superposition of all the uncorrelated plane waves can then be applied as prescribed nodal pressures on the cavity's open surface (see [22]). …”

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“…A FE model was presented in Refs. 19 and 20 to compute the vibroacoustic response of curved panels; however, the model is not appropriate for large scale structures as it requires much computational cost.…”

Reduction of the sound transmission of a periodic sandwich plate using the stop band concept

“…The mechanical properties of these plates offer a distinct advantage in weight over other commonly used construction materials, such as rib stiffened plates. However, the high stiffness-to-mass ratio can result in supersonic wave propagation at relatively low frequencies and imparts poor acoustical performance [1,2].…”

“…Abundant work concerning the mechanical properties, the dynamic model, and the vibration and sound properties of sandwich structures have been conducted [1][2][3][4][5][6][7][8][9][10].…”