noun
half-awake voice; sleepy voice
Describes the groggy, slurred, or mumbling voice of someone who has just woken up or is still drowsy.
朝、寝ぼけ声で「おはよう」と言った。
In the morning, I said 'good morning' in a sleepy voice.
電話に出たら、まだ寝ぼけ声だった。
When I answered the phone, my voice was still half-awake.
Compound of 寝ぼけ (drowsiness, half-asleep state) + 声 (voice).