Spectral analysis of muscular sound at low and high contraction level.
The activated muscle generates a low frequency rumbling noise, which is known as the Sound-MyoGram (SMG). Spectral analysis of the SMG is carried out in this work, in order to: (i) check the adequacy of both the Fast Fourier Transform (FFT) and the Maximum Entropy Spectrum Estimation (MESE). Because it is a well known technique, the FFT method is only briefly described, while the philosophy of the MESE method is given in more detail and completed with a description of the recursive algorithm; (ii) select a frequency parameter suitable to describe the SMG. For this purpose two well-defined physiological conditions (20% and 80% Maximal Voluntary Contraction) have been adopted in order to provide a safe reference for the interpretation of the findings. The results show that: (a) both FFT and MESE are adequate to estimate the SMG Power Spectrum; (b) both the mean and the median frequency are suitable parameters, the mean frequency being the more favourable one; (c) the SMG Power Spectrum is a promising tool to study the muscle activation modalities.
Diemont
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Dipartimento di Elettronica, Politecnico di Milano, Italy.
Figini
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Orizio
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Perini
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Veicsteinas
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D000328:Adult; D005583:Fourier Analysis; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D009119:Muscle Contraction; D013016:Sound; D013018:Sound Spectrography / Q000379:methods