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09.07 Low Frequency Noise Control

Low frequency vibration suppression of a moderate thick cabin structure by multiple piezoelectric patches shunted with RL-double negative capacitance circuits
Time: 6:40 pm

Author: Zhiwei Zheng

Abstract ID: 1807

Multiple piezoelectric patches shunted with RL-double negative capacitances circuits, which are bonded on the bulkhead, are proposed to control the resonant response of multiple low frequency modes of a moderate thick cabin structure. Dynamic modeling of the electromechanical coupling system of the cabin structure and the piezoelectric shunt circuit is established by employing the three-dimensional finite element. Optimum tuning strategy is based on the trial and error method. It is shown that the proposed approach is effective in enhancing the generalized electromechanical coupling coefficient and controlling the low frequency modes that exhibits coupled deformation of the bulkhead and cabin structure.

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Low-frequency noise control using layered granular aerogel and limp porous media
Time: 6:20 pm

Author: Yutong Xue

Abstract ID: 2215

The acoustic absorption of granular aerogel layers with a granule sizes in the range of 2 to 40 ?m is dominated by narrow-banded, high absorption regions in the low-frequency range and by reduced absorption values at higher frequencies. In this paper, we investigate the possibility of developing new, low-frequency noise reduction materials by layering granular aerogels with traditional porous sound absorbing materials such as glass fibers. The acoustic behavior of the layered configurations is predicted using the arbitrary coefficient method, wherein the granular aerogel layers are modeled as an equivalent poro-elastic material while the fibrous media and membrane are modeled as limp media. The analytical predictions are verified using experimental measurements conducted using the normal incidence, two-microphone impedance tube method. Our results show that layered configurations including granular aerogels, fibrous materials, and limp membranes provide enhanced sound absorption properties that can be tuned for specific noise control applications over a broad frequency range.

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Theoretical and numerical study of nonlinear acoustic absorbers for low frequency noise control
Time: 7:00 pm

Author: Yang Min

Abstract ID: 3171

In this paper, the sound absorption characteristics of cubic nonlinear sound-absorbing structures are analyzed by theoretical and numerical methods. The slow flow equations of the system are derived by using complexification averaging method, and the nonlinear equations which describe the steady- state response are obtained. The resulting equations are verified by comparing the results which respectively obtained from complexification-averaging method and Runge-Kutta method. It is helpful to optimize the structural parameters and further improve the sound absorption performance to study the variation of the sound absorption performance of cubic nonlinear structure with its structural parameters.

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3D printed multifunctional, load-bearing, low-frequency sound absorbers
Time: 1:00 pm

Author: Bhisham Sharma

Abstract ID: 3177

Cellular porous materials are an attractive choice for lightweight structural design. However, though their open porous architecture is ideally suited for multifunctional applications, their use is typically limited by the pore sizes achievable by traditional as well as advanced fabrication processes. Here, we present an alternative route towards overcoming this pore size limitation by leveraging our recent success in printing fibrous structures. This is achieved by superimposing a fibrous network on a load-bearing, open-celled porous architecture. The multifunctional structure is 3D printed using a novel technique that enables us to simultaneously print a load-bearing scaffold and the necessary fibrous network. The acoustic properties of the printed structures are tested using a normal-incidence impedance tube method. Our results show that such structures can provide very high absorption at low frequencies while retaining the mechanical performance of the underlying architected structure.

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