Chapter 7: The value of humility (paragraph 17)

The tenth step of humility teaches that we should not be given to empty laughter on every least occasion because: a fool's voice is for ever raised in laughter.

(Para. 17 of Ch. 7 of Saint Benedict's Rule, trans. by Patrick Barry OSB, 1997.)

I think that if there's empty laughter, there must also be full laughter -- laughter of the soul, full of delight in life, full of joy.  Maybe soul-laughter is even silent sometimes.