I think you can play the sound when "Touch End".
If you want to calculate the speed(v).
You have the distance(S) between 1st position to the last position.
And the time of swipe by adding dt while touching(t).
So you will have v = S / t.
When touch end, you can compare the v with any number X and do the action.
Very good , thank you !!Maverick1912
One thing tho, the game itself will not make the player end touch often, since you have to swipe alot in a circle, any tip on this to make a lasting slash sound effect?EDIT: I used Touch speed ,thanks for the help !