noun
sound of laughter; laughing voice
Refers to the audible sound of someone laughing, not the act of laughing itself.
隣の部屋から笑い声が聞こえた。
I heard laughter from the next room.
彼女の笑い声はとても明るい。
Her laugh is very cheerful.
笑い is the general noun for laughter or a laugh, while 笑い声 specifically refers to the sound of laughing.
Compound of 笑い (wara-i, 'laughing') + 声 (koe, 'voice').