An Innovation In Real-Time Acoustic Holography

实时声全息技术的创新

• 批准号: 9802847
• 负责人: Sean Wu
• 金额: $ 18.99万
• 依托单位: Wayne State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-06-01 至 2001-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9802847&HistoricalAwards=false
• 关键词: Innovation; Real; Time; Acoustic; Holography

This GOALI project is being carried out in collaboration with the Advanced Engineering Center of Ford Motor Company. The objectives of this investigation are two-fold: (1) to develop an innovative methodology to reconstruct the acoustic pressure fields accurately and cost-effectively, and (2) to extend this methodology to producing real-time acoustic holography that enables one to visualize the instantaneous acoustic pressure distributions and their evolution as the excitation forces change with time. The novelty of the methodology lies in the fact that the acoustic pressures are reconstructed through an expansion of acoustic modes, or a set of particular solutions to the Helmholtz equation. The coefficients associated with these acoustic models are determined by requiring the assumed form solution to satisfy pressure boundary conditions at measurement points. The errors incurred in this process are minimized by using the least squares method. The significance of this methodology is that solutions thus obtained are unique and the efficiency of numerical computations is high. This is because the acoustic modes employed represent a complete set of eigenfunctions that satisfy the Helmholtz equation. The number of acoustic modes determines the measurement points, which is small when a right coordinate system is selected for the source geometry under consideration. Hence numerical computations are fast and efficient. Moreover, the acoustic pressure is written as an explicit form of the acoustic modes. Therefore the time-domain signals can be obtained by taking a direct inverse Fourier transformation. This makes the generation of real-time acoustic holography possible. The investigation will yield an effective tool for diagnosing both structure and airborne noise sources. Using this tool, the design engineers can acquire a better understanding of the noise generation mechanisms, assess the noise performance of a complex machine cost-effectively, and develop effective measures to circumvent vibration and noise problems. This tool will also significantly enhance the teaching effectiveness in classroom education. It will enable students to `see` the radiation, reflection, and diffraction of sound waves, thus making the learning of complex acoustic concepts easier, and more interesting and effective.

该GOALI项目正在与福特汽车公司的先进工程中心合作进行。本研究的目标是双重的：（1）开发一种创新的方法来重建声压场准确和具有成本效益，和（2）扩展这种方法来产生实时声全息，使人们能够可视化的瞬时声压分布和它们的演变随着激励力随时间的变化。该方法的新奇在于，声压重建通过扩展的声学模式，或一组特定的解决方案的亥姆霍兹方程。与这些声学模型相关联的系数通过要求假定形式的解满足测量点处的压力边界条件来确定。在此过程中产生的误差最小化，通过使用最小二乘法。这种方法的重要性在于所得解是唯一的，数值计算效率高。这是因为所采用的声学模式表示满足亥姆霍兹方程的本征函数的完整集合。声学模式的数量决定了测量点，当为所考虑的源几何形状选择正确的坐标系时，测量点的数量很小。因此，数值计算是快速和有效的。此外，声压被写为声学模式的显式形式。因此，时域信号可以通过采取直接逆傅立叶变换来获得。这使得实时声全息的产生成为可能。该研究将为结构噪声源和空气噪声源的诊断提供一个有效的工具。使用该工具，设计工程师可以更好地了解噪声产生机制，经济有效地评估复杂机器的噪声性能，并制定有效的措施来规避振动和噪声问题。这一工具也将大大提高课堂教育的教学效果。它将使学生“看到”声波的辐射，反射和衍射，从而使复杂的声学概念的学习更容易，更有趣和有效。