Finger snapping

Snapping (or clicking) one's fingers is the act of creating a snapping or clicking sound with one's fingers. Primarily this is done by building tension between the thumb and another (middle, index, or ring) finger and then moving the other finger forcefully downward so it hits the palm of the same hand at a high speed. Alternatively, one can press the middle finger and thumb together and then fling the index finger into them.

Physics

There are three components to the snapping finger sound: (1) The "friction" or "sliding" sound between the second (middle) finger and the thumb (2) The "impact" sound from the second finger colliding with a groove created by contacting the third (ring) finger with the palm and (3) The "pop" sound from the rapid compression and subsequent decompression of air. The third "pop" sound is the most audible of the three components and because it is caused by a compression of air between the fast moving second finger and the groove between the palm and third finger, the second finger must hit both the palm and a small portion of the top of the third finger in order to get the full "snap" sound. If the second finger only hits the palm, only the first two components will be heard and there will be a significant reduction in the total "snap" sound. This usually happens because the third finger is simply not in contact with the palm, but it can also happen if the third finger doesn't align properly with the striking point of the second finger. In this case, no part of the second finger lands anywhere on top of the third finger and ends up only hitting the palm.