Semi-active control of smart porous structure for sound absorption enhancement

Abstract

For sound absorption of conventional porous materials, its noise-reducing ability in low frequencies is less than that in high frequency bands. A porous layer offers effective sound absorption when the thickness of layer is a quarter wavelength of the sound wave. Increasing the layer thickness is not an effective solution. Adjustment of rear air cavity volume for the porous medium has been used in practical applications to increase low frequency sound absorption. Noise reduction using only passive sound absorption characteristics is a challenge, especially when the operation conditions of noise source changes. In this study, we propose a smart porous material having noise reduction ability in the broad frequency band. We implement semi-active control by applying a magnetic reactive material to a porous medium. The smart foam proposed in this study reduced noise with adjustment of the magnitude and polarity of the magnetic field. Evaluation of its noise reduction performance is performed with the impedance tube method. Experiments are conducted for semi-active noise control of the proposed smart foam. The sound absorption characteristics are controlled efficiently with relatively low electric power consumption. A theoretical model to predict absorption characteristics is proposed using the transfer-matrix method, and its results show good agreement with measured behaviors.

Magnetic and Tunable Sound Absorption Properties of an In-Situ Prepared Magnetorheological Foam

“…However, the efficiency and sound absorption performance of passive noise control materials are poorer at lower-frequency ranges (20–200 Hz) [ 14 ], compared to that of active materials, for which extra energy consumption is inevitable [ 6 , 13 , 15 ]. Some challenges in using passive noise control materials are primarily related to the long wavelength of sound at low-frequency levels, which results in poor sound absorption [ 16 ].…”

Development and Prospect of Smart Materials and Structures for Aerospace Sensing Systems and Applications

“…It can be expected that other fillers, such as ZnO and graphene, will be used to improve the piezoelectric response. Similarly, in order to improve the problem of the low efficiency of smart foam in the low-frequency region, Kim et al [ 53 ] proposed to integrate the magnetic reaction material into the intelligent porous structure and realized the low-frequency efficiency improvement through a semi-active control scheme. Similarly, a sliding mode control can also be used for vibration and noise control to improve the robustness of the system, and Talebitooti et al [ 54 ], based on a nonlinear sliding mode control method, achieved effective suppression of the vibration sound of cylindrical shells by optimizing the position of the piezoelectric actuator.…”

Folk Music Audio Enhancement Method Combining Internet of Things and GA

“…e read speed of the multiplexer is also output by the decay time control, which decays by about 10% per read. e music signal after the initial equalization processing by the audio analyzer is transmitted to the processing center through the Internet of ings for the actual ethnic sound enhancement processing [23][24][25].…”