Abstract
A beamforming technique is introduced to measure the normal acoustic impedance at both normal and oblique incidence in a free field. In the proposed method, microphone array signals are decomposed into incident and reflected waves using an adaptive nulling algorithm, which is a type of beamforming algorithm. The acoustic impedance can then be calculated from the ratio of these two signals. To obtain better results, the pressure vector commonly used in array signal processing is replaced with the transfer function vector between each microphone, and the white Gaussian noise is suppressed by a wavelet shrinkage technique. For an accurate experimental setup, the incident and reflected angles are estimated by the multiple signal classification method with spatial smoothing. The experiments conducted in a semi-anechoic room show that the proposed method is efficient and accurate in measuring the normal acoustic impedance of sound-absorbing materials under a free field condition.
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References
ASTM E1050 Standard test method for impedance and absorption of acoustical materials using a tube, two microphones and a digital frequency analysis system, ASTM, E1050-EBGL (1998).
J. F. Allard and B. Sieben, Measurements of acoustic impedance in a free field with two microphones and a spectrum analyzer, J. Acoust. Soc. Am. 77(4) (1985) 1617–1618.
Y. Champoux, J. Nicolas and J. F. Allard, Measurement of acoustic impedance in a free field at low frequencies, Journal of Sound and Vibration, 125(2) (1988) 313–323.
M. Tamura, Spatial Fourier transform method of measuring reflection coefficients at oblique incidence. I: Theory and numerical examples, J. Acoust. Soc. Am. 88(5) (1985) 2259–2264.
M. Tamura, J. F. Allard and D. Lafarge, Spatial Fourier-transform method for measuring reflection coefficients at oblique incidence. II: Experimental results, J. Acoust. Soc. Am. 97(4) (1995) 2255–2262.
R. Lanoye, G. Vemeir, and W. Lauriks, Measuring the free field acoustic impedance and absorption coefficient of sound absorbing materials with a combined particle velocity-pressure sensor, J. Acoust. Soc. Am. 119(5) (2006) 2826–2831.
Y. J. Kang and E. S. Hwang, Beamforming-based Partial Field Decomposition in NAH, Journal of Sound and Vibration, 314 (2008) 867–884.
T. -J. Shan, M. Wax and T. Kailath, On spatial smoothing for direction-of-arrival estimation of coherent signals, IEEE Transactions on Acoustics, Speech and Signal Processing, ASSP-33 No. 4 (1985) 806–811.
M. R. Bai and J. Lee, Industrial noise source identification by using an acoustic beamforming, system Transactions of ASME, 120 (1998) 426–433.
Y. -Y. Shih, J. -C. Chen and R. -S. Liu, Development of wavelet de-noising technique for PET images, Computerized Medical Imaging and Graphics, 29 (2005) 297–304.
Y. Y. Kim and J.-C., Hong Frequency response function estimation via a robust wavelet de-noising method, Journal of Sound and Vibration, 244(4) (2001) 635–649.
A. Bakhtazad, A. Palazoglu and J. Romagnoli, Process trend analysis using wavelet-based denoising, Control Engineering Practice 8 (2000) 657–663.
Y. J. Kim, Y. J. Kang and J. S. Kim, Parameters estimation and performance prediction of acoustical materials, ICSV 12 Proceedings (2005).
Y. J. Kang, Studies of Sound Absorption by and Transmission through Layers of Elastic Noise Control Foams: Finite Element Modeling and Effects of Anisotropy, Ph.D. dissertation, School of Mechanical Engineering, Purdue University (1994).
J. C. Liberti Jr. and T. S. Rappaport, Smart antennas for wireless communications: IS-95 and Third Generation CDMA Applications, Prentice Hall, Upper Saddle River, (1999) 257–260.
D. H. Johnson and D. E. Dudgeon, Array signal processing: concepts and techniques, Prentice-Hall, Englewood Cliffs, NJ (1993).
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This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo
Jongcheon Sun received his B.S. degree in Mechanical Engineering from Korea University, Korea, in 2002. He is currently in the Unified Master’s and Doctor’s course at the School of Mechanical and Aerospace Engineering at Seoul National University, Korea. His research areas are acoustic holography and beamforming.
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Sun, J.C., Shin, C.W., Ju, H.J. et al. Measurement of the normal acoustic impedance using beamforming method. J Mech Sci Technol 23, 2169–2178 (2009). https://doi.org/10.1007/s12206-009-0435-z
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DOI: https://doi.org/10.1007/s12206-009-0435-z