Antonyms of groan:
cheering, laughing, smiling, exultation, rejoicing, cackle, chortle, chuckle, giggle, guffaw, laugh, snicker, snigger, titter, twitter.
Examples of usage:
  1. This took place on the 6th of the Ninth Month, about 20 minutes past 2, without sigh or groan, even as a lamb.
    "Memoir and Diary of John Yeardley, Minister of the Gospel", John Yeardley.
  2. Then there was a groan which struck even Aby's ear; but Sir Thomas was still alive and listening, and so he went on.
    "Castle Richmond", Anthony Trollope.
  3. Then I felt rather than heard the father's groan.
    "John Halifax, Gentleman", Dinah Maria Mulock Craik.