Combined plots of all the coughs produced by the 20 healthy volunteers.

<p>These demonstrate the cough airflow dynamic parameters measured in these experiments. <b>A</b>: cough ‘propagation distance-velocity-time’; <b>B:</b> ‘2-D projected area-expansion rate-time’. The parameters digitized directly from the recorded images (propagation distance and 2-D area) are shown by solid red lines with the actual data points as empty circles, with reference to the left y-axis, labeled with the red font. The derived parameters (velocity and 2-D area expansion rate) are shown by thinner, dotted blue lines, with reference to the right y-axis, labeled with the blue font.</p

Characteristics of the 20 healthy human volunteers used in the cough imaging.

<p>Characteristics of the 20 healthy human volunteers used in the cough imaging.</p

Experimental set-up of the shadowgraph imaging system.

<p>Schematic of the layout with the large, 1-m diameter, spherical concave f/5 mirror and subject test area at one end, and the high-speed camera with the LED light-source and the image capture system (laptop) approximately 10 m away at the other end of the environmental chamber. Note that the schematic diagram has been shown previously to describe this experimental set-up <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034818#pone.0034818-Tang1" target="_blank">[8]</a>.</p

A shadowgraph still image of a cough captured from video.

<p>This demonstrates the typical bifurcation of the cough air-stream as a volunteer coughs into his sleeve.</p