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轿车车内200Hz以下的低频噪声非常恼人,它主要是由结构振动引起的,所以研究结构声腔的耦合机理非常重要。而结构声腔的耦合主要包括振型耦合以及频率耦合两个方面,其中振型耦合可用振型耦合系数描述。首先基于腔内声压计算公式,获得了仅适用于规则结构或者声腔的振型耦合系数的解析计算公式。而对于不规则对象,推导并验证了一种振型耦合系数的新的数值计算方法。然后重点分析了某简单结构声腔耦合系统的振型耦合系数特征,发现结构声腔的振型相似系数和振型复杂系数是影响振型耦合系数的关键,振型相似系数越高、振型复杂系数越低,则振型耦合系数越大、结构声腔耦合程度越强,这就是某简单结构声腔耦合系统的振型耦合机理。
The low frequency noise below 200Hz in a car is very annoying. It is mainly caused by the structural vibration. Therefore, it is very important to study the coupling mechanism of the structure acoustic cavity. However, the coupling of the structure acoustic cavity mainly includes the mode coupling and the frequency coupling, and the mode coupling can be described by the mode coupling coefficient. First, based on the calculation formula of the sound pressure inside the cavity, the analytic formula of the coupling coefficient of the mode shape that is only applicable to the regular structure or sound cavity is obtained. For irregular objects, a new numerical calculation method of mode coupling coefficient is derived and verified. Then the characteristics of mode coupling coefficient of a simple structure acoustic cavity coupling system are analyzed emphatically. It is found that the mode shape coefficient and the mode shape complex coefficient of the structure acoustic cavity are the key factors affecting the mode coupling coefficient. The higher the mode shape similarity coefficient is, The lower the coupling coefficient is, the stronger the acoustic coupling is. This is the mode coupling mechanism of a simple structure acoustic cavity coupling system.