FPGA-based implementation of steerable parametric loudspeaker using fractional delay filter

Abstract Parametric loudspeaker enables high directivity sound along the radiation direction to be generated by the nonlinear effects of ultrasonic waves in air. Based on the theory of phased array, the beams of parametric loudspeakers can be steered to other directions. In this paper, the Fractional Delay (FD) filter is introduced to generate any arbitrary delay to accurately control the steering angle of the beam. Field Programmable Gate Array (FPGA) is a better choice for the system of steerable parametric loudspeaker due to its strong capability of parallel and real-time processing. The algorithms have been realized easily and quickly by combining the tools of Matlab simulink and DSP Builder. Finally, the validity of the system is verified through comparing the theoretical simulations with the experimental results.

[1]  M. Yoneyama,et al.  The audio spotlight: An application of nonlinear interaction of sound waves to a new type of loudspeaker design , 1983 .

[2]  C. W. Farrow,et al.  A continuously variable digital delay element , 1988, 1988., IEEE International Symposium on Circuits and Systems.

[3]  David T. Blackstock,et al.  Parametric array in air , 1975 .

[4]  Unto K. Laine,et al.  Splitting the Unit Delay - Tools for fractional delay filter design , 1996 .

[5]  H. O. Berktay,et al.  Possible exploitation of non-linear acoustics in underwater transmitting applications , 1965 .

[6]  G. Oetken.  A new approach for the design of digital interpolating filters , 1979 .

[7]  Yijun Shi.  Modeling of acoustic waves for linear phased arrays , 1998 .

[8]  Gerald D. Cain,et al.  Offset windowing for FIR fractional-sample delay , 1995, 1995 International Conference on Acoustics, Speech, and Signal Processing.

[9]  Yoshio Yamasaki,et al.  Acoustic Projector Using Directivity Controllable Parametric Loudspeaker Array , 2010 .

[10]  D. Grant,et al.  Efficiency of low power audio amplifiers and loudspeakers , 2001, IEEE Trans. Consumer Electron..

[11]  Woon-Seng Gan,et al.  FPGA implementation of parametric loudspeaker system , 2004, Microprocess. Microsystems.

[12]  Unto K. Laine,et al.  Splitting the unit delay [FIR/all pass filters design] , 1996, IEEE Signal Process. Mag..

[13]  Woon-Seng Gan,et al.  Beamwidth Control in Parametric Acoustic Array , 2005 .

[14]  Vesa Välimäki,et al.  Principles of fractional delay filters , 2000, 2000 IEEE International Conference on Acoustics, Speech, and Signal Processing. Proceedings (Cat. No.00CH37100).

[15]  Klaus Linhard,et al.  Steerable highly directional audio beam loudspeaker , 2005, INTERSPEECH.

[16]  C. Sidney Burrus.  Multiband least squares FIR filter design , 1995, IEEE Trans. Signal Process..

[17]  H. O. Berktay,et al.  Farfield performance of parametric transmitters , 1974 .

[18]  Woon-Seng Gan,et al.  A digital beamsteerer for difference frequency in a parametric array , 2006, IEEE Transactions on Audio, Speech, and Language Processing.

[19]  P. J. Westervelt.  Parametric Acoustic Array , 1963 .

[20]  Mark F. Hamilton,et al.  Parametric array in air: Distortion reduction by preprocessing , 1998 .