SNR Improvement of an Optical Wave Microphone Using a Wavelet Network

Part of the Advances in Intelligent Systems and Computing book series (AISC, volume 273)


In this paper, we discuss an approach of S/N ratio improvement for an optical wave microphone. With the optical wave microphone, ultra-weak diffraction light; which is resulting from phase modulation from a sound wave, is converted to an electrical signal using a light detector. In this way the optical wave microphone can detect the sound without making any contact with others. Signal intensity could be increased or S/N ratio could be improved with (1) optical method, (2) method using electrical circuit, or (3) method using information processing. In this study, we adopted wavelet network as one of the methods using information processing. As a result we succeeded noise reduction at low frequency using only proposed algorithm, not by using combination of various filters.


optical wave microphone laser wavelet network convex wavelet 


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  1. 1.
    Sonoda, Y., Akazaki, M.: Measurement of Low-Frequency Ultrasonic Waves by Fraunhofer Diffraction. Jpn. J. Appl. Phys. 33(pt. 1, 5B), 3110–3114 (1994)Google Scholar
  2. 2.
    Sonoda, Y.: Direct detection of acoustic waves by laser light diffraction and proposals of the optophone. In: Proc.16th Int. Cong. on Acoust. and 135th Meet. of Acoust. Soc. America, vol. 1, pp. 427–428 (1996)Google Scholar
  3. 3.
    Goodman, J.W.: Introduction to Fourier Optics, 3rd edn. Roberts & Company Publishers (2005)Google Scholar
  4. 4.
    Evans, D.E., von Hellermann, M., Holzhauer, E.: Fourier optics approach to far forward scattering and related refractive index phenomena in laboratory plasmas. Plasma Phys. 24, 819–834 (1982)CrossRefGoogle Scholar
  5. 5.
    Sonoda, Y., Suetsugu, Y., Muraoka, K., Akazaki, M.: Applications of the Fraunhofer-diffraction method for plasma-wave measurements. Plasma Phys. 25, 1113–1132 (1983)CrossRefGoogle Scholar
  6. 6.
    Tanaka, K., Nogami, G., Sonoda, Y.: Measurement of Audible Acoustic Wave by Laser Light. The Transactions of the Institute of Electrical Engineers of Japan 122-E(7), 362–368 (2002)Google Scholar
  7. 7.
    Morlet, J., Arens, G., Fourgeau, E., Giard, D.: Wave Propagation and Sampling Theory - Part 1: Complex Signal and Scattering in Multilayered Media. Geophysics 47(2), 203–221 (1982)CrossRefGoogle Scholar
  8. 8.
    Morlet, J., Arens, G., Fourgeau, E., Giard, D.: Wave Propagation and Sampling Theory - Part 2: Sampling Theory and Complex Waves. Geophysics 47(2), 222–236 (1982)CrossRefGoogle Scholar
  9. 9.
    Yamakawa, T., Uchino, E., Samatsu, T.: Wavelet Neural Networks Employing Over Complete Number of Compactly Supported Non-Orthogonal Wavelet and Their Applications. In: Proc. IEEE Int. Conf. on Neural Networks, pp. 1391–1396 (1994)Google Scholar
  10. 10.
    Yamakawa, T., Uchino, E., Samatsu, T.: The Wavelet Network Using Convex Wavelets and Its Application to Modeling of Dynamical Systems. The Transactions on the IEICE J79-A(12), 2046–2053 (1996) (in Japanese)Google Scholar

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© Springer International Publishing Switzerland 2014

Authors and Affiliations

  1. 1.Graduate School of Industrial EngineeringTokai UniversityKumamotoJapan

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