Noise is one of the most common concerns we hear at site surveys — “will it be too loud to sleep?” and “will the outdoor unit annoy the neighbours?” are near-universal questions. Here is an honest guide to what modern air conditioning systems sound like.
How Noise Is Measured — dB(A)
Air conditioning noise is measured in dB(A) — decibels weighted to approximate human hearing sensitivity. The scale is logarithmic — 30dB is not twice as loud as 15dB but approximately 8 times as loud. Some reference points:
- 15dB: Barely perceptible — the sound of a quiet library
- 20dB: Very quiet — a whisper at 1 metre
- 25dB: Quiet — leaves rustling, a quiet bedroom at night
- 35dB: Audible — quiet conversation in a room
- 45dB: Clearly audible — background conversation
- 50dB: Moderate — quiet office environment
Indoor Unit Noise — Minimum Fan Speed
The indoor unit noise at minimum fan speed is the most relevant figure for bedroom use. Here is how the major brands compare:
- Mitsubishi Electric MSZ-LN 25: 19dB(A) — below the threshold of most people’s hearing in a quiet room
- Daikin Perfera 25: 20dB(A) — effectively inaudible
- Fujitsu ASYG-LLCE 25: 20dB(A) — very quiet
- Mitsubishi Electric MSZ-AP 25: 21dB(A) — very quiet
- Samsung WindFree Comfort 25: 22dB(A) — good, plus no airflow sensation
- Daikin Sensira 25: 22dB(A) — good
- LG Standard Plus 25: 26-28dB(A) — audible in a quiet bedroom to most people
For reference, a quiet bedroom at night is approximately 25-30dB of ambient noise. Units at 19-22dB are below the ambient noise level of the room — effectively inaudible. Units at 26-30dB are at or slightly above the ambient level — perceptible to many people.
Outdoor Unit Noise
Outdoor unit noise matters for two reasons: potential complaints from neighbours, and placement near windows or outdoor seating areas. Modern outdoor units typically run at 45-55dB(A) at 1 metre when working hard (hot day, full cooling demand). At 5 metres, this reduces to approximately 37-48dB(A).
A standard outdoor unit running at moderate load produces noise roughly equivalent to a quiet conversation or a low-volume television — clearly audible if you are standing next to it, much less noticeable at conversational distance.
Minimising Noise Impact
Position outdoor units away from bedroom windows: The most effective measure. A unit 5 metres from a bedroom window on the opposite wall produces minimal impact on sleeping.
Avoid solid enclosures: Boxing in outdoor units to “hide” them reduces airflow and makes the unit work harder, increasing noise. If screening is needed for aesthetic reasons, open-sided screening with adequate airflow clearance is appropriate.
Anti-vibration mounts: Outdoor units on wall brackets can transmit vibration through the building fabric. Anti-vibration mounts on the bracket significantly reduce this. We include these as standard on all bracket-mounted outdoor units.
Call 07833 053749 or contact us for a free site survey where we discuss unit positioning and noise specifically for your property.