Enkhmurun

I drive RX400h 2007. I have 2 problems.

The first is on heating system. When starting my car at the end of working day at about 6 am, it is typically about -25C. At the same time if I start a heating system there is sound seems like whispering and if i increase a fan speed the sound become loader and vise versa. What i noticed is that the sound is not outside and it is inside and near a interior air filter. After driving 15-20 minutes this annoying sound is gone. I think it is because of the cold temperature and something liquid used for the heating system if there is such thing.

The another issue is related to an engine I think. When I am driving and then abruptly or instantly increasing the speed, there is sound like opening and closing a valve. After just starting or stopping the car and then pushing a speed pad abruptly, there is no such sound. Also when driving without instant speed , it is fine. Though I had my car's engine and motor oil replaced roughly a month ago, I think it is not a reason.

Please help me. Thank you.