This is a sound effect of Yawn. This sounds like someone is yawning. It is a female yawn.

Six versions are included full:

File A – Yawn (Version 1) 0:04
File B – Yawn (Version 2) 0:04
File C – Yawn (Version 3) 0:05
File D – Yawn (Version 4) 0:03
File E – Yawn (Version 5) 0:03
File F – Yawn (Version 6) 0:03