Voiceless sounds are produced with the ligamental folds and the arytenoids held wide enough apart to allow regular non-turbulent airflow between them.

Play the top movie to see voiceless [s], and note the V-shape of the open folds. Notice that the space between the folds is not as wide as it is for normal breathing.

Now play the lower movie to see the folds switch between voiceless mode and voiced mode.

Notice that, strictly speaking, voicelessness isn’t really a type of phonation, it’s more the absence of it.

English sounds produced using voiceless mode include;

[p] in port, [f] in fort, [t] in taught, [θ] in thought, [k] in caught, and [s] in sort.

In English, each of these sounds is contrasted with its ‘voiced’ partner [b, v, d, ð, g, z]. Many languages have two series of sounds (usually stops, fricatives and affricates), where the basis for contrast is voiceless versus voiced.