Weird sound, not the normal one, from Prius when turning off

Hello All,
I have a Prius 2008, and recently I can hear a weird sound after turning off the engine. This sound is not like the normal sound which I used to hear previously which I think is related to the pump.
I feel like the pump is struggling to do what it's supposed to do.
I recorded the sound and added a link to it, it is like zzzzz sound.

Note: sometimes I hear the sound when turning on the car, but for very few seconds.

Any help is appreciated!
Thanks
Wishes

 

Thank You for your responses, I had the car checked by a mechanic, and after listening to the sound, he said it is "coolant Heat pump" and there is no big harm if I leave it without replacement now; however, today (after two days) the sound disappeared, but the Hybrid system and check engine alerts appeared!
I had the car tested by another mechanic, he read the error codes, then told me it is the Hybrid battery! and that the "coolant Heat pump" is running fine.
so it seems I am going for a battery replacement now...