Sound radiation of complex mode shapes

复杂振型的声辐射

• 批准号: 256895788
• 负责人: Professor Dr.-Ing. Michael Sinapius
• 金额: --
• 依托单位: Institut für Systemleichtbau
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2015-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/256895788?language=en
• 关键词: Sound; radiation; complex; mode; shapes

The effective suppression of noise pollution requires the precise knowledge of the noise generating sources. Nowadays a profound and consolidated basic knowledge on vibroacoustics exists. Sources of noise are mainly characterized by vibration amplitude, spectral content, and frequency dependent radiation capability. The latter was investigated in detail in terms of structural mode shapes because the dynamic response of structures is determined by mode shapes. The related research is mainly based on the assumption of homogenously distributed structural damping and simple boundary conditions which simplifies the underlying differential equations. Then the related eigenproblem yields real normal modes. This assumption is valid for many applications and delivers sufficiently accurate results. However, the increasing application of high performance light weight structures made from fiber reinforced plastics simultaneously increase the acoustic requirements and, in consequence measures for acoustic damping. The latter are located at critical structural points for weight-saving reasons which violates the assumption of homogenously distributed structural damping. Consequently the structural resonances are determined by modes of complex shapes, i.e. forward waves instead of standing waves. Boundary condition may cause these complex mode shapes as well. The existence of complex modes raises the question of their influence on sound radiation.The basic hypothesis of the project is that the grade of complexity of complex mode shapes caused by non-proportional damping has a significant influence on the sound radiation below the coincidence frequency. The sound radiation characteristics should by describable by a complex radiation coefficient. The project will systematically investigate the relation between the mode shape complexity and the sound radiation.

有效地抑制噪声污染需要对噪声产生源有准确的认识。如今，振动声学的基础知识已经非常深刻和巩固。噪声源的主要特征是振动幅度、频谱含量和频率相关辐射能力。由于结构的动力响应是由结构的振型决定的，因此，本文从结构振型的角度对结构的动力响应进行了详细的研究。相关的研究主要是基于结构阻尼均匀分布的假设和简单的边界条件，简化了基本微分方程。然后，相关的特征值问题产生真实的正常模式。这个假设对许多应用都是有效的，并提供足够准确的结果。然而，由纤维增强塑料制成的高性能轻质结构的日益增加的应用同时增加了声学要求，并因此增加了声学阻尼措施。后者位于关键的结构点的重量节省的原因，违反了均匀分布的结构阻尼的假设。因此，结构共振由复杂形状的模式决定，即前向波而不是驻波。边界条件也可能导致这些复杂的振型。复模态的存在提出了复模态对声辐射影响的问题，本课题的基本假设是：非比例阻尼引起的复模态振型的复杂程度对重合频率以下的声辐射有显著影响。声辐射特性可用复辐射系数来描述。本计画将系统研究振型复杂度与声辐射之关系。

项目成果

Numerical and Experimental Study of Sound Power Reduction Performance of Acoustic Black Holes in Rectangular Plates

• DOI: 10.4271/2015-01-2270
• 发表时间: 2015-06
• 期刊: SAE International Journal of Passenger Cars - Electronic and Electrical Systems
• 作者: Oliver Unruh;Christopher Blech;H. Monner

Sound Radiation Properties of Complex Modes in Rectangular Plates: A Numerical Study

• DOI: 10.3813/aaa.918805
• 发表时间: 2015
• 期刊: Acta Acustica United With Acustica
• 作者: Oliver Unruh;M. Sinapius;H. Monner

Influence of inhomogeneous damping distribution on sound radiation properties of complex vibration modes in rectangular plates

• DOI: 10.1016/j.jsv.2016.05.009
• 发表时间: 2016-09
• 期刊: Journal of Sound and Vibration
• 影响因子: 4.7
• 作者: Oliver Unruh;Oliver Unruh

Parametric Study of Sound Radiation Properties of Complex Vibration Patterns in Rectangular Plates using an Analytical Model

• DOI: 10.3813/aaa.918866
• 发表时间: 2015-07
• 期刊: Acta Acustica United With Acustica
• 作者: Oliver Unruh