Regarding a sound from A/C system, I need your observations and comments.
When I start the A/C, apart from the air fan sound, I also hear a very low and continuous sound in background. Of course this is more hearable when air fan is low. It is like a ups sound but in a low level. It goes away after some time after shutting off the A/C.
I don’t remember if I heard this in tests, maybe I didn’t pay much attention at that time. Is it same for anybody else? Can it be the heat pump?
Cabin is so quiet so we can hear all the details.
That is also a disadvantage in a way. 
When I start the A/C, apart from the air fan sound, I also hear a very low and continuous sound in background. Of course this is more hearable when air fan is low. It is like a ups sound but in a low level. It goes away after some time after shutting off the A/C.
I don’t remember if I heard this in tests, maybe I didn’t pay much attention at that time. Is it same for anybody else? Can it be the heat pump?
Cabin is so quiet so we can hear all the details.