Too scared to sleep...

It's been almost 2 hours now... I heard something clearly and can't sleep, so I'm writing here. Around 1 AM, before going to bed, I went to the kitchen... It's quiet outside because it's the middle of the night, but from beyond the curtains, I clearly heard "Fu, fuｯ"...! The sound was like laughter, but not quite, which made it even scarier. Beyond the curtains is the balcony, but I'm on the 4th floor. For reference, the curtains are about 1M from where I was. It wasn't from outside the window on the balcony, but from really close behind the curtain... My neighbor also has a woman living there, but it wasn't from that far away; I really heard it from right behind the curtain... I was so startled, I froze, my breath catching, thinking "Huh?" I didn't have the courage to open the curtains.