Slaptongue
For me this effect works best on low notes, you can hear King Curtis doing it on King Curtis & Champion Jack Dupree - Blues at Montreux
Place the surface of your tongue flat against the reed and finger a low note. It should feel like if you try to move it away there is a vacuum between your tongue and the roof of your mouth. Now quickly pull the tongue off the reed while blowing hard.
This effect was also common for musical passages in the early part of the twentieth century, especially in some danceband and vaudeville styles.