This Lennox XP17-036 heat pump is a solar powered unit. You can hear how quiet it is in this informal video by comparing the unit's noise level to that of the birds chirping in the trees or to the fence gate creaking in the background. It is running at full capacity cooling a home of approximately 3500 square feet. Other models can heat or cool up to 5000 square feet per unit.
We had installed a 4 ton unit in another nearby home and it was equally as quiet. The owner was expecting to hear a certain noise level from her unit and asked "When is that big boy going to turn on?" I wish I had a video of her face when we told her that it was already running.