When i unlock ny car and get in, I can hear a faint but noticable noise coming from the cabin of the car. I can hear it before and after i turn the engine on/off.(its always when the engine is off). It only sounds for a few seconds then stops. I dont know if any one has any ideas?
On my car (Jaguar x type) there is a very small fan close to the instruments that samples the cabin air for the heater / AC, what you describe sounds just like mine.
However, they are normally almost inaudible - perhaps it needs a clean but be very careful they are delicate. Don't use a garage airline :) but one of the electronic air puffers may work.
On my different car (2016 Toyota RAV4 hybrid), I also hear a similar buzzing noise after unlocking the door. The noise is almost surely some kind of electric motor, but the question is, where?
In the case of my car, I assume it is the brake booster electric pump. So it is not coming from the cabin of the car; it occurs under the hood. The reason an electric brake booster pump is needed is that the car is a hybrid, and thus, does not always run the engine when in motion, but brakes need to be ready to be operated always.
Is your car perhaps a diesel? If so, it doesn't have manifold vacuum and a pump is needed for the brake booster. So, it could be brake booster vacuum pump you're hearing.