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A study of active control techniques for noise reduction in an aircraft fuselage model.

机译：飞机机身模型中用于降噪的主动控制技术的研究。

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摘要

A simplified cylindrical model is used to investigate the elementary mechanisms of control of sound transmission into aircraft cabins by two active control techniques: propeller synchrophasing and active vibration control. Propeller synchrophasing involves controlling the relative rotational phase of the engines to achieve maximum cabin noise reduction. Active vibration control involves structurally controlling the vibrational response of the cabin wall to reduce the important modes which transmit their energy into the cabin.;Noise reductions for harmonic excitation at acoustic cavity resonance are shown to be in excess of 20 dB throughout most of the cavity whether synchrophasing or active vibration control is used. Off-resonance reductions are substantially less due to increased modal density requiring a larger number of actuators for effective control of the complex sound field. Additional studies were performed using synchrophasing in conjunction with active vibration control to study their joint capabilities in controlling complex sound fields. The dual control system displayed improved control performance with noise reductions on the order of 25-35 dB and a more uniform sound field. Also, the complementary control characteristics of the system clearly demonstrated effective control of orthogonal acoustic modes of the cavity. However, the improved effectiveness of the control system was dependent upon judiciously positioning the actuators for optimal control of the sound field.;An independent study was performed to identify the effects of a complex geometry on sound transmission into an aircraft fuselage model interior. For this study, a geometrically scaled cabin floor was installed in the unstiffened test cylinder to investigate the structural and acoustic influence of the simulated cabin floor. Results indicated that the stiffening of the cylindrical model associated with insertion of the floor strongly influenced the structural response of the cylinder but generally had little effect on the coupled pressure response. Conversely, the modification of the interior acoustic cavity tended to have little influence on the cylinder response but substantially reduced the coupled pressure response.;Thus, this investigation identified the fundamental mechanisms of control of sound transmission into simplified models of aircraft fuselages by active control techniques.
机译：一个简化的圆柱模型被用来研究通过两种主动控制技术来控制声音传递到飞机机舱的基本机制：螺旋桨同步定相和主动振动控制。螺旋桨同步定相包括控制发动机的相对旋转相位，以最大程度地降低机舱噪音。主动振动控制涉及从结构上控制机舱壁的振动响应，以减少将能量传递到机舱中的重要模式。在整个腔体内，声腔共振时谐波激励的噪声减小超过20 dB。是否使用同步调相或主动振动控制。由于模态密度的增加，需要大量的执行器来有效地控制复杂的声场，因此，失谐的减小明显较少。使用同步定相结合主动振动控制进行了其他研究，以研究它们在控制复杂声场方面的联合能力。双控制系统显示出改进的控制性能，降噪幅度达25-35 dB，声场更均匀。同样，系统的互补控制特性清楚地证明了腔体正交声模的有效控制。然而，控制系统的改进效果取决于明智地定位致动器以实现对声场的最佳控制。进行了一项独立研究，以确定复杂几何形状对声音向飞机机身模型内部的传递的影响。对于本研究，将几何比例缩放的机舱地板安装在未加劲的测试缸中，以研究模拟机舱地板的结构和声学影响。结果表明，与地板插入相关的圆柱模型的刚度强烈影响圆柱的结构响应，但通常对耦合压力响应影响很小。相反，对内部声腔的修改对气缸响应几乎没有影响，但会大大降低耦合压力响应。因此，本研究通过主动控制技术将控制声音传输的基本机制确定为飞机机身的简化模型。

著录项

  • 作者

    Jones, James D.;

  • 作者单位

    Virginia Polytechnic Institute and State University.;

  • 授予单位 Virginia Polytechnic Institute and State University.;
  • 学科 Mechanical engineering.
  • 学位 Ph.D.
  • 年度 1987
  • 页码 302 p.
  • 总页数 302
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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