模态及尺寸参数对封闭腔内声压的影响研究

Study on Impacts of Modal and Dimensional Parameterson Interior Sound Pressure of Enclosed Cavities

为掌握影响车内低频声压的关键参数及其影响规律,以快速有效控制车内低频噪声,基于封闭腔内声压的计算公式,对模态参数、尺寸参数与声压响应的关系进行了分析.首先获得腔内声压可直接用公式计算的研究对象和计算公式;其次通过分析公式中的可变输入量,找出影响腔内声压的主要模态参数、尺寸参数,采用仅改变某一参数而保持其余参数为初始值的方法,逐个计算分析这些参数对腔内声压的影响规律,找出影响腔内声压的关键参数及其影响规律,并通过试验进行了验证;最后利用关键参数及其影响规律对某型轿车的车内低频噪声进行控制,快速、成功将其车内低频声压降低到目标范围内.研究结果表明:腔内声压的关键参数是结构振型的节线数、结构板厚;增加1条节线,即结构增加1个“+”加强筋或加强梁,或增加结构板厚,可降低腔内声压;以此研究结论为指导,在某型轿车的车身薄弱位置添加加强筋后,原超出目标范围的峰值声压降低了约10 dB,快速降低到目标范围以内,从而为车内低频噪声的快速控制提供一条新思路.

In order to understand the critical influencing parameters and their impact rules on car interior low-frequency sound pressure,and to control car interior low-frequency noise rapidly and effectively,the relationship between modal and dimensional parameters and interior sound pressure was analyzed based on the equation of interior sound pressure of enclosed cavities.Firstly,the object whose interior sound pressure could be directly calculated by equations and the equations for calculating the interior sound pressure were acquired.Next,through analyzing the input variables in these equations,the major modal and dimensional parameters that impact the interior sound pressure were spotted.By changing one parameter only and keeping the others in their original values,the impact of each parameter on interior sound pressure was computed and analyzed.Then the critical impact parameters and their impact rules on interior sound pressure were achieved,which were consequently verified by experiments.Finally,when the impacting parameters and their impact rules were applied in the control of a notchback's interior low-frequency noise,the interior sound pressure was lowered below the target quickly and successfully.The above results indicated that node line number of structure modes and structure thickness are the critical impacting parameters of interior sound pressure and that adding 1 node line,which is adding 1+shaped rib or stiffener on the structure,or increasing structure thickness can decrease interior sound pressure.Guided by these conclusions,a test was made in which strengthening ribs were added on the weak area of a car body,and the peak sound pressure that was originally above the target was soon lowered by about 10dB,which is below the target.