Forward propagation of time evolving acoustic pressure: formulation and investigation of the impulse response in time-wavenumber domain.
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.
Grulier
Vincent
V
Ecole Nationale Superieure d'Ingenieurs du Mans, rue Aristote, 72085 Le Mans Cedex 09, France.
Paillasseur
Sébastien
S
Thomas
Jean-Hugh
JH
Pascal
Jean-Claude
JC
Le Roux
Jean-Christophe
JC
D000162:Acoustics; D003198:Computer Simulation; D005583:Fourier Analysis; D008962:Models, Theoretical; D011312:Pressure; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors