Ecole Nationale Superieure d'Ingenieurs du Mans, rue Aristote, 72085 Le Mans Cedex 09, France.
J Acoust Soc Am. 2009 Nov;126(5):2367-78. doi: 10.1121/1.3216916.
The aim of this work is to continuously provide the acoustic pressure field radiated from nonstationary sources. From the acquisition in the nearfield of the sources of a planar acoustic field which fluctuates in time, the method gives instantaneous sound field with respect to time by convolving wavenumber spectra with impulse response and then inverse Fourier transforming into space for each time step. The quality of reconstruction depends on the impulse response which is composed of investigated parameters as transition frequency and propagation distance. Sampling frequency also affects errors of the practically discrete impulse response used for calculation. To avoid aliasing, the impulse response is low-pass filtered with Chebyshev or Kaiser-Bessel filter. Another approach to implement the impulse response consists of applying an inverse Fourier transform to the theoretical transfer function for propagation. To estimate the performance of each processing method, a simulation test involving several source monopoles driven by nonstationary signals is executed. Some indicators are proposed to assess the accuracy of the temporal signals predicted in a forward plane. The results show that the use of a Kaiser-Bessel filter numerically implemented or that of the inverse Fourier transform can provide the most accurate instantaneous acoustic signals.
这项工作的目的是连续提供非稳态声源辐射的声压场。从声源近场采集随时间波动的平面声场，该方法通过将波数谱与脉冲响应卷积，并在每个时间步逆傅里叶变换到空间，从而给出随时间的瞬时声场。重建质量取决于由研究参数（如过渡频率和传播距离）组成的脉冲响应。采样频率也会影响用于计算的实际离散脉冲响应的误差。为避免混叠，使用切比雪夫或凯泽-贝塞尔滤波器对脉冲响应进行低通滤波。实现脉冲响应的另一种方法是对传播的理论传递函数应用逆傅里叶变换。为了评估每种处理方法的性能，执行了涉及由非稳态信号驱动的几个单极子声源的模拟测试。提出了一些指标来评估前向平面中预测的时间信号的准确性。结果表明，使用数值实现的凯泽-贝塞尔滤波器或逆傅里叶变换可以提供最准确的瞬时声信号。
