Ripple
: to move in small waves
: to pass or spread through or over (someone or something)
“He laughs. A rippling sound like Sethe’s sons make when the tumble in hay or splash in rain water” (Morrison, 266)
Meaning in the context, the laugh is similar to the sound generated by the quick fall of rain.
Source: http://www.merriam-webster.com/dictionary/rippling
