Journal of applied physiology
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An objective and accurate measurement and characterization of breath sounds was carried out by a fast-Fourier-transform frequency-domain analysis. Normal vesicular breath sounds, picked up over the chest wall of 10 healthy subjects showed a characteristic pattern: the power of the signal decreased exponentially as frequency increased. ⋯ The maximal frequencies of inspiratory and expiratory breath sounds, picked up over the base of the right lung, were (in Hz +/- SD) 446 +/- 143 and 286 +/- 53 (P less than 0.01), over the base of the left lung 475 +/- 115 and 284 +/- 47 (P less than 0.01), over the interscapular region 434 +/- 130 and 338 +/- 77 (P less than 0.05), and over the right anterior chest 604 +/- 302 and 406 +/- 205 (P less than 0.05). Breath sounds picked up over the trachea were characterized by power spectra typical to a broad spectrum sound with a sharp decrease of power at a cut-off frequency that varied between 850 and 1,600 Hz among the 10 healthy subjects studied.