Practical absorption limits of MPP absorber |
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作者姓名: | MAA Dah-You |
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作者单位: | Institute of |
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基金项目: | Acknowledgement Mr. Tong Xiaopeng prepared the Figs. 1 and 2. |
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摘 要: | The construction and properties of microperforated panel (MPP) absorber are discussed. The absorption limit of the absorber had been shown that low values of the perforate constant k = d(f/10)1/2 and the orifice diameter d (in mm) are essential for MPP to have high absorption in wide frequency band. To find the exact limits, take 1 for k as a start, because both specific resistance and high absorption require k around one. And the orifice diameter d is chosen as 0.1 mm, so that the peak absorption coefficient (resonance absorption) is at 1000 Hz, and high sound frequency may be in the absorption region. Is it possible for a single layer of such an MPP to cover the whole absorption region required in practice? The half-absorption limit is not a good criterion, because low absorption comes in also in some cases. The 0.5 absorption coefficient limit is suggested for practical region, as a standard for comparison. Absorption curves were drawn for different load resistances, of absorption coefficients versus frequency. Ordinary MPP absorber absorbs in slightly over two octaves, and the new absorber with r = 1 (specific resistance equal to the characteristic impedance in air)is slightly better than these, 2.5 octaves. The new absorbers with r > 1, are much better than these, and some satisfies high absorption in broad frequency range. Realization of these will mean great progress of MPP absorbers.
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关 键 词: | 实际吸收极限 MPP材料 声学材料 孔口直径 |
收稿时间: | 2006-08-08 |
修稿时间: | 2006-08-08 |
Practical absorption limits of MPP absorber |
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Authors: | MAA Dah-You |
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Institution: | Institute of Acoustics, The Chinese Academy of Sciences Beijing 100080 |
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