Journal of Ocean Engineering and Technology (한국해양공학회지)

Korean Society of Ocean Engineers (한국해양공학회)
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Implementation of Noise Reduction Methodology to Modal Distribution Method

  • Received : 2011.01.12
  • Accepted : 2011.04.22
  • Published : 2011.04.30
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Abstract

Vibration-based Structural Health Monitoring (SHM) systems use field measurements of operational signals, which are distorted by noise from many sources. Reducing this noise allows a more accurate assessment of the original "clean" signal and improves analysis results. The implementation of a noise reduction methodology for the Modal Distribution Method (MDM) is reported here. The spectral subtraction method is a popular broadband noise reduction technique used in speech signal processing. Its basic principle is to subtract the magnitude of the noise from the total noisy signal in the frequency domain. The underlying assumption of the method is that noise is additive and uncorrelated with the signal. In speech signal processing, noise can be measured when there is no signal. In the MDM, however, the magnitude of the noise profile can be estimated only from the magnitude of the Power Spectral Density (PSD) at higher frequencies than the frequency range of the true signal associated with structural vibrations under the additional assumption of white noise. The implementation of the spectral subtraction method to MDM may decrease the energy of the individual mode. In this work, a modification of the spectral subtraction method is introduced that enables the conservation of the energies of individual modes. The main difference is that any (negative) bars with a height below zero after subtraction are set to the absolute value of their height. Both noise reduction methods are implemented in the MDM, and an application example is presented that demonstrates its effectiveness when used with a signal corrupted by noise.

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References

  1. Berouti, M., Schwartz, R. and Makhoul, J. (1979). "Enhancement of Speech Corrupted by Acoustic Noise", Proceeding of IEEE International Conference on Acoustics, Speech, and Signal Processing, Vol 4, pp 208-211.
  2. Boll, S. (1979). "Suppression of Acoustic Noise in Speech Using Spectral Subtraction", IEEE Transactions on Acoustics, Speech and Signal Processing, Vol 27, pp 113-120. https://doi.org/10.1109/TASSP.1979.1163209
  3. Choi, M. (2009). The Modal Distribution Method: A New Statistical Algorithm for Analyzing Measured Response, Thesis (PhD), Texas A&M University.
  4. Godsill, S.H. and Rayner, P.J. (1998). Digital Audio Restoration: A Statistical Model Based Approach, Secaucus, NJ, USA, Springer-Verlag Inc.
  5. Loizou, P.C. (2007). Speech Enhancement: Theory and Practice, Boca Raton, FL. CRC Press.
  6. Schless, V. and Class, F. (1998). SNR-dependent Flooring and Noise Overestimation for Joint Application of Spectral Subtraction and Model Combination, Proceeding of the 5th International Conference on Spoken Language Processing.
  7. Sweetman, B. and Choi, M. (2009). The Modal Distribution Method for Statistical Analysis of Measured Structural Response, Journal of Probabilistic Engineering Mechanics.
  8. Sweetman, B. and Choi, M. (2006). The Modal Distribution Method: A New Statistical Algorithm for Analyzing Measured Acceleration Data, Proceedings of SPIE, Volume 6174, page 61742H-1, San Diego, California, USA. https://doi.org/10.1117/12.658024