Transmission sounding of human lungs by complex acoustic signals

摘要

Laboratory installation for acoustic sounding of human lungs by complex signals has been developed. Linear frequency sweep signal (80-1000 Hz, 20 s) and the signal containing m-coded (the basis - 511 readouts) phase-manipulated fragments with three various carrying frequencies (200, 300, 750 Hz) are entered into mouth. Pilot experiment has been carried out with 3 volunteers. Results of processing of sounding signals received on the chest surface by convolution method show, that the pictures of arrivals of sounding signal are various above the top, middle and basal areas of lungs, and have steady (replicating from attempt to attempt and from one kind of signals to another) specific features connected with time delays of arrivals, ratio of amplitudes of maxima of arrivals. In basal areas of lungs two various arrivals of both sounding signals have been directly found. This testifies to existence, at least, two various ways of sound transmission in human lungs, distinguished on resulting sound velocity of mechanical oscillations. Subject's individuality, dependent on body build and age related condition of lung parenchyma, was found both in time delays between emission of sounding signal and reception of the first arrival, and time delays between the first and the second arrivals. The developed method seems to be promising for non ionizing transmission low frequency acoustic tomography of lungs.