In this figure, time amplitude plots of a single breath are displayed as they appear at multiple sites in a subject with no lung disease. Twelve microphones are placed on the back; numbers 1 through 6 are on the right side, 9 through 14 are on the left. There is one on each lateral base - microphone numbers 7 and 15 respectively. There is one over the heart (number 8) and one over the trachea - number 16. Waveforms are presented in both the unexpanded (top) and expanded (bottom) modes. The unexpanded waveform shows one full breath. The unexpanded and expanded waves corresponding to the same channel are shown in the same color. The choice of colors is arbitrary. The solid bars under the unexpanded waves mark respiratory cycle - green bars indicate inspiration and blue bars indicate expiration. The arrow indicates the location of the expanded interval. The duration of the expanded interval is 100 milliseconds. You can listen to the sound at any site by clicking the mouse at that site.

In this normal subject, there are no wheezes and no crackles. The time amplitude pattern seen over the chest is relatively uniform from site to site. Note the longer and louder waveform over the tracheal microphone as compared to those over the chest wall.