Create two variables, Last Position as Vector and Distance as Float. On Pawn movement (or Event Tick), calculate GetActorLocation - Last Position. The length of this vector is the moved distance. Add it to Distance and check whether Distance > Stride Length. If so, make a foot step sound and subtract Stride Length from Distance, so you are ready for the next step. Of course this only makes sense with Thumbstick locomotion, not with teleportation.