Forward propagation of time evolving acoustic pressure:Formulation and investigation of the impulse response intime-wavenumber domain

摘要

The aim of this work is to continuously provide the acoustic pressure field radiated fromnonstationary sources. From the acquisition in the nearfield of the sources of a planar acoustic fieldwhich fluctuates in time, the method gives instantaneous sound field with respect to time byconvolving wavenumber spectra with impulse response and then inverse Fourier transforming intospace for each time step. The quality of reconstruction depends on the impulse response which iscomposed of investigated parameters as transition frequency and propagation distance. Samplingfrequency also affects errors of the practically discrete impulse response used for calculation. Toavoid 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 Fouriertransform to the theoretical transfer function for propagation. To estimate the performance of eachprocessing method, a simulation test involving several source monopoles driven by nonstationarysignals is executed. Some indicators are proposed to assess the accuracy of the temporal signalspredicted in a forward plane. The results show that the use of a Kaiser–Bessel filter numericallyimplemented or that of the inverse Fourier transform can provide the most accurate instantaneousacoustic signals.