What Scout hears coming from the Radley house after she rolls into their yard in a tire is someone laughing.
There's an excerpt on Chapter four of to kill a mocking bird, where it is mentioned
And I quote "Through all the head-shaking, quelling of nausea and Jem-yelling, I had heard another sound, so low I could not have heard it from the sidewalk. Someone inside the house was laughing"
