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.
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.
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.
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.