Learning to Beatbox? Here is the Human Beatbox Sound Archive entry for the Front Tongue Smack
Name: Front Tongue Smack
Family: Tongue Clicks (N)
Description: This sound is made by bringing the the tip of the tongue up to the front of the hard palate, creating suction between the two surfaces, then pulling the tongue down. It is similar to the sound made with the work tsk, as in a reprimand, "tsk tsk tsk." This is technically considered a click though it has less of a sharp sound than many other clicks.
Other Links: About the Human Beatbox Archives and Notation System