clack 
(klăk)
(klăk)v. clacked, clack·ing, clacks
v.intr.
1. To make an abrupt, sharp sound, as in the collision of two hard surfaces.
2. To chatter thoughtlessly or at length.
3. To cackle or cluck, as a hen.
v.tr.
To cause to make an abrupt, sharp sound.
n.
1. A clacking sound: the clack of an old-fashioned typewriter.
2. Something that makes a clacking sound.
3. Thoughtless, prolonged talk; chatter.
[Middle English clakken, from Old Norse klaka, of imitative origin.]
clacker n.