when your middle finger releases from your thumb.

The sound occurs when my middle finger releases from my thumb.

There is SOME sound when my middle finger releases from my thumb, but the majority of the sound occurs when my middle finger hits the palm of my hand.

A common misconception is that it is your thumb hitting your index finger, but it is actually your middle finger hitting the base of your thumb.

I agree with Ptrask, here are my reasons why: 1. When I put paint on my middle finger, and snapped my fingers, there was a blue spot the whole way down my thumb. This gives the impression that the finger actually never loses contact with the thumb. This may just be the way that I snap my fingers, however. 2. Try snapping while your hand is wet, the water acts as a lubricant and eliminates the friction. A snapping sound can still be made, telling us that the friction between the thumb and the finger is not the cause. 3. Try Ptrask's experiment of putting a cloth (or something else soft) at the base of your thumb where your finger would reside after you snap your fingers. This muffles the noise, meaning the collision between the finger and the base of your thumb is an important factor in creating the sound. 4. Try getting a finger from one hand, and rub it on the thumb from the other hand, try this at any (or every) speed you can. If no noise is created, this reinforces the findings of point 2. 5. Get a book, and push it across a smooth surface, it makes a quiet scraping sound, now slam the book into the ground. Notice the rubbing makes a quiet noise that sounds nothing like a snap, but slamming noise is much louder with a sound somewhat similar sound to the snapping of your fingers. This demonstrates how the sort of sounds that the snapping of your fingers makes is more likely to be from a collision than from rubbing.

OK that was a fun question, there's a whole group of people now behind me in my lounge getting annoyed trying to figure that out. (Saturday night in New Zealand - what can I say). The general consensus seems to be the sound comes from your finger hitting your palm.

let's do a little experiment shall we? I think i have conclusive results :) Looking at this problem there are two ways to research it: can I make the snapping sound by hitting my finger against my palm at the same speed, and can i make the sound without hitting my palm. (scientific research is invalid unless repeatable, so i'll say everything i do) First i tried hitting the part of my palm I normally hit but now without snapping my fingers. When i try it i get no sound, nothing substantial at least, possibly because i can't build up enough speed. Then i tried the second option: snapping my fingers without hitting my palm. It doesn't work, i don't have the control to stop my finger from hitting my palm unless i do it less powerfully, in which case i think i don't have the speed necessary for making the sound loud enough. so that approach doesn't work well. Next I tried it in another way: my other hand. With my right hand i grab my pinky and ring-finger in such a way that my right-hand thumb is positioned in front of the left-hand middlefinger. Now snapping my finger built up the same speed and power, but after snapping my middlefinger would NOT hit my palm (equal conditions except the tested factor). The sound is low, merely from the bit of friction. So now we know my right-hand thumb does NOT produce sound when snapped against my left-hand middlefinger. This in itself can be conclusive, but not until i've tested that there is no difference between using my right-hand thumb instead of my left for making the snapping-sound. So next I tried by repositioning my right-hand thumb to snap my left-hand middlefinger with my right-hand thumb in such a way that i DO hit my left-hand palm. After some practice (as i did in all these previous attempts) i managed to get the well-known snapping sound out of it! voila, there we have it: my left hand can make the snapping sound using my right hand just as wel as using one hand alone, but it can NOT produce sound when i DON'T hit my left palm. Apparently the most sound is produced from hitting the palm!

The first one. Before it hits your hand. ;D

Doesn't the sound come in that mili-second between the release and the hit? The sound is produced because the action broke the sound barrier. The same as a jet flying.

The sound is produced because the action is fast enough to break the sound barrier. Just like a jet. It doesn't hit anything either.

I uh... can't snap my fingers >.>