Answers
How loud is a ductless mini split?
Indoor heads are quiet at low fan speed and audible at high. Where to find the manufacturer’s published dB(A) rating, and how placement decides whether the outdoor unit bothers you or your neighbor.
The short answer
Quieter than the ducted furnace it replaces, and quieter than a window air conditioner, but not silent. Indoor heads are close to inaudible on low fan and clearly audible on high. Every manufacturer publishes a sound-pressure rating in dB(A) per fan speed on the submittal sheet, so ask for that page rather than trusting an adjective.
Ask for the submittal sheet
Sound-pressure ratings are published per model, per fan speed, for both the indoor head and the outdoor unit, measured at a stated distance. That is the only comparable number in this conversation, and it is free to obtain. If a bid names a decibel figure without saying which fan speed it belongs to, it is not telling you anything.
What you will actually hear indoors
The sound of an indoor head is moving air, not machinery, and it rises and falls as the inverter modulates. On a mild Bellingham evening the system loafs along at low speed and disappears into the room. On a 19°F morning recovering the house from a setback, it runs the fan hard and you will notice it. That is one more argument for holding a steady setpoint instead of deep nightly setbacks.
Bedrooms and offices deserve a deliberate choice
In a bedroom the complaint is rarely volume, it is a fan cycling up while you are trying to sleep. Placement high on a wall where the airflow is not blowing across the pillow helps, and so does selecting a head sized to the room rather than the largest one on the multi-zone list. Sizing a bedroom head correctly keeps it in its quiet range most of the night.
The outdoor unit and your property line
Compressor noise carries, and a narrow older city lot can put your outdoor unit a few feet from a neighbor’s bedroom window. We site it away from sleeping rooms on both properties, on a solid pad or wall bracket rather than a resonant deck, with clearance for airflow. If you are inside city limits, check whether a noise standard applies before you commit to a location.
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