こえ
voice
koe
JMdict 1380440
いいgoodこえ声voiceだね
The i-adjective いい (nice) sits directly before the noun 声こえ (voice) it describes. The plain copula だ (is) states it casually, and the final ね (right?) invites agreement — “a nice voice, isn’t it?” — turning a remark into something shared.
hanamaru