Basic Lung Sounds

In this section the most commonly encountered lung sounds will be presented. They will first be described. They then can be played by pressing the play button. The time amplitude plots of the sounds will also be displayed as shown in the illustration below. Time amplitude plots of lung sounds are generally made in two ways: expanded or unexpanded. The unexpanded method is similar to a phonocardiographic time amplitude display. This allows an overall view of the acoustic characteristics in real time. In the time expanded analysis the time or x-axis is stretched out so that details of the acoustic phenomena can be examined more carefully. Time domain plots are illustrated in both the time unexpanded and time expanded modes. It is clear that the pattern differences between different types of lung sounds are seen more easily in the expanded mode.

Amplitude-versus-time plots of typical lung sounds, showing that the expanded time scales in the right column reveal visually distinct patterns not readily seen in the plots at conventional speeds on the left.

Time is on the horizontal axis, and amplitude on the vertical axis. The plots on the right, reproduced here at a scale of 400 mm per second, are 0.1 sec long and are sections from the 0.8-sec-long plots on the left shown here at 50 mm per second.

Reprinted with permission from “Visual lung-sound characterization by time-expanded wave-form analysis”, R. Murphy, S. Holford, and W. Knowler, New England Journal of Medicine, 296:968-971, April 28, 1977.