Practical absorption limits of MPP absorber

来源 :Chinese Journal of Acoustics | 被引量 : 0次 | 上传用户:lxkef
下载到本地 , 更方便阅读
声明 : 本文档内容版权归属内容提供方 , 如果您对本文有版权争议 , 可与客服联系进行内容授权或下架
论文部分内容阅读
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. 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 c oefficients 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.
其他文献
农村税费改革是中央解决“三农”问题的一项重要决策,它对于规范农村收入分配制度、建设农村小康社会、减轻农民负担具有重要的作用和意义,但同时也导致了不可忽视的县乡财政
马基雅维利与孟子都是世界上伟大的政治思想家,虽然他们的时代、地域不同,但都处在各自时代社会变革的转折点上,他们的思想都各在东西方产生了深远的影响.马基雅维利主张性恶
期刊
信息化时代下,“互联网+”模式正在逐渐应用到实验教学改革实践中.随着虚拟实验技术的不断成熟和进步,受资金和条件的限制,地方开放大学系统各专业(特别是理工类专业),传统的
在金融学科建设领域的研究和实践中,我国金融体制改革的步伐正逐渐从宏观的理论研究角度转入微观实施和操作.文章对金融学科建设的背景、人才的素质要求以及学科建设分层次教
【摘要】二连盆地储层渗透率一般在1×10-3u㎡,有的甚至只有0.1×10-3u㎡。孔隙度平均10%,岩心实验表明80%吼道在0.1um,粘土含量在10-20%,且主要以蒙脱石为主,粘土膨胀性大,储层低孔、低渗特征明显,80%探井需压裂改造来认识储层。以往国内外研究表明针对该类储层低伤害的压裂技术成为该类储层改造的关键。通过多年的研究与实践,逐步形成了新型的综合低伤害压裂技术,具体表现在液体材料上
【摘要】近年来,随着地质勘测技术的不断发展,相关学者及科研机构对于盆地古生界的考究越来越重视。本文就柴达木盆地古生界油苗的发现及地质意义问题对古生界烃源岩进行了介绍,对柴北缘石炭系烃源岩与油气关系进行了分析,并就古生界中的油气苗进行了概述。  【关键词】柴达木盆地 古生界油苗 地质意义  我们知道,柴达木盆地的古生界广泛被认为是盆地的基底,一直没有引起人们的关注。近年来,研究发现柴达木盆地的古生界
期刊
探析国际金融危机给我国商业银行带来的影响,就是要汲取国际金融危机的经验教训,避免重蹈覆辙.加强在金融危机背景下商业银行投资风险控制,是有效规避经营风险、提高银行经营
上次我遇见莱娜尔的时候,她整个人都是蓝色的.她身上到处都是海洋,甚至连那些不应该是海洋的地方也是,而且她的手指是大海的手指,长得很长,还是蓝色的.