This is a heat pump. We assume this is all there is to it. That's not the case. In many cases it is really half a heat pump. The other half in many systems is a "air handler" that lives inside the house. This is all good and proper if the installation is done correctly.
The air handler is usually not especially noisy but it does make a sound. It cycles on and off.
And if the installation is not correct it can drive you nuts! So before you install a heat pump, check where the air handler will go. If it's in the attic (it often is) be sure that the installer has checked for noise issues.