Sound Absorption Of Micro-perforated Panel Research Articles

Sound absorption theory for micro-perforated panel with petal-shaped perforations.

Micro-perforated panel (MPP) absorbers with circular perforations are used in many noise control applications due to their attractive wide-brand sound absorption performance. Different from a common MPP with circular perforations, a unique type of MPP absorber with petal-shaped perforations is proposed. The sound absorption theory for the MPP with petal-shaped perforations is developed by accurately considering the fluid velocity in the petal-shaped perforation hole. This theory can account for the effect of altered perforation morphology (from circular to petal) on sound absorption. Finite element simulations are performed to validate the proposed theory, with good agreement achieved. The sound absorption of MPP with petal-shaped perforations is compared with that of the traditional MPP with the same porosity. It is demonstrated that the change in hole shape significantly modifies the fluid velocity field and the flow resistivity in/of the hole, and hence the sound absorption of the proposed MPP with petal-shaped perforations can outperform that of the traditional MPP in the considered case. This work proposes a general MPP theory that not only contains the classical Maa's theory for circular MPP, but also accounts for the MPP with petal-shaped perforations.

Effect of Fabric Layer on Sound Absorption of Micro-Perforated Panel

Micro-Perforated Panel (MPP) absorber becomes an alternative to common fibrous porous absorber without owning health and environmental issues. The system is considered as the next generation of absorber in noise control. However, such a system suffers from narrow absorption bandwidth so that its application becomes limited. Theoretically, the frequency range with effective absorption is determined by the surface acoustic impedance controlled by the perforation ratio, hole diameter and cavity depth. Hence, by keeping those parameters to be constant, an intervention to the change of impedance is expected to be useful in widening the absorption bandwidth. In this research, textile materials from woven fabrics namely cotton fabric, plain fabric and satin fabric were used to cover the surface of Micro Perforated Panel (MPP) absorber either at the front or at the back surface. The sound absorption coefficients were measured for the normal incidence using an impedance tube. From the measured results, it is found that the presence of the fabric on MPP surface can improve the MPP absorber in terms of amplitude as well as the frequency bandwidth of absorption. Moreover, the placement of the woven fabric at downstream area is more beneficial than at the upstream area.

Sound absorption of microperforated panel with L shape division cavity structure

Microperforated panel (MPP) absorbers have been widely used in noise reduction and are regarded as a promising alternative to the traditional porous materials. However, the absorption bandwidth of a single-layer MPP with limited cavity space is insufficient to compete with the porous materials. In order to improve the sound absorption ability of the single-layer MPP with limited cavity space, MPP with L shape division cavity structure is introduced. Based on the MPP and electro-acoustical equivalent circuit principle, sound absorption properties of MPP with L shape division cavity are studied. Simulation and experimental results show that MPP with L shape division structure have better sound absorption performance than MPP with single cavity structure. Building on L shape division cavity, the extended plate can further improve the sound absorption of MPP. Wide band sound absorption of MPP can be realized with limited cavity space.

Sound absorption of microperforated panel mounted with helmholtz resonators

Microperforated panel (MPP) absorbers have been widely used in noise reduction and are regarded as a promising alternative to the traditional porous materials. However, the absorption bandwidth of a single-layer MPP is insufficient to compete with the porous materials. In order to improve the sound absorption ability of the single-layer MPP, MPP mounted with Helmholtz resonators (MPPHR) is introduced. Based on the MPP, Helmholtz resonators theory and electro-acoustical equivalent circuit principle, sound absorption properties of MPPHR are studied. Simulation and experimental results show that MPPHR have two peak frequencies and one anti-resonant frequency. The low-frequency peak is dependent on the Helmholtz resonators, while the high frequency peak is close to the peak of the single-layer MPP. The low-frequency sound absorption peaks move to low frequency with the neck length and the volume of Helmholtz resonators increasing. The high-frequency sound absorption peaks move to high frequency with the volume of Helmholtz resonators cavity increasing. Multiple Helmholtz resonator parallel MPP structure can provide more sound absorption than single MPPHR at low frequency range due to the introduction of more additional sound absorption peaks.

Sound Absorption Analysis of Micro Perforated Panel with Ladder Change Type Cross Section

A kind of variable cross section micro perforated panel (MPP) with ladder micro porous is introduced in this paper. Based on the double layers MPP theory and neglected the effect of cavity between two layers of MPP, sound absorption model of MPP with ladder micro porous is established. Numerical simulations are carried out to predict the sound absorption of MPP with ladder micro porous. The predicted results show good agreement with measurements. Through analyzing the weight to the sound-absorbing of orifice size, this study also points out that the smaller orifices play the major role in the sound absorption.

Sound Absorption of Micro-Perforated Panel

and profile of micro-perforated single-, double-, and triple-layer systems with varying panel parameters were calculated by using the lumped and the distributed models for acoustic impedances. The sound absorption levels and profiles predicted by using the distributed model with Maa’s acoustic impedance showed a close agreement for all panel systems with those obtained experimentally by using impedance-tube and reverberation-room tests.