Alteration in the low frequency lung sounds in respiratory disorders associated with crackles.

Lung sounds were recorded in three groups of 5 subjects, 2 conditions associated with pulmonary crackling (asbestosis and pulmonary oedema), and in normal non-smoking males. A technique was used which permitted extraction and analysis of the low-frequency sounds. Differences were evident in the 5-50 Hz range of the frequency spectra which allowed separation of all 3 groups. A prominent feature was the close similarity of the low-frequency sounds within the asbestos group when plotted on a scattergram. The findings suggest that alteration in low-frequency breath sound occurs in parenchymal lung disease and that its potential merits further investigation.