Some lung diseases (e.g., pneumonia) can be recognized by experienced clinicians before a radiographic finding is available. Several pathologic changes in the lung, which produce characteristic sounds, can be detected more readily by auscultation than by radiography because of the convenience and availability of the stethoscope ( 1). It gives direct information about the structure and function of the lung that cannot be obtained with any other simple and noninvasive method ( 2-6). However, on the basis of large individual variations, these small changes ( Δ Q ∼ 5%, SD(Q) ⩾ ± 5%) have no clinical significance and need not to be considered in the automatic detection of lung diseases by analyzing lung sounds.Īuscultation of the lung is an important and simple diagnostic method ( 1). For both men and women, a slight increase of the relative power in the frequency band of 330 to 600 Hz was recorded with increasing age. Within the groups, a small but significant correlation existed between Q and age (r 2 ⩽ 0.1, p < 0.05).

Significant differences in Q were found in men versus women (p < 0.05), but not in smokers versus nonsmokers. Linear regression analysis was used as a measurement of age-dependence of these variables. In order to describe the power spectrum of the lung sounds, we calculated mean and median frequency, frequency with the highest power, and a ratio (Q) of relative power of the two frequency bands of 330 to 600 Hz and 60 to 330 Hz.

The data were analyzed according to age, sex, and smoking habit. To investigate these changes, we recorded lung sounds taken from four locations in the posterior thorax of 162 subjects, together with airflow. Systematic changes in breathing sounds with increasing age are of diagnostic importance. Auscultation is one of the most important noninvasive and feasible methods for the detection of lung diseases.

Bronchial breath sounds