How Loud Is an Air Conditioner? (50–75 dB)

How an air conditioner compares to other sounds

Indoor and outdoor parts sound very different

An air conditioner has two main noise sources: the fans that move air and the compressor that pumps refrigerant. In a split system the compressor and its fan sit in the outdoor unit, so the room mainly hears the indoor fan. Window and portable units put everything in one box inside or in the window, which is why they are usually much louder in the room.

The outdoor unit still matters. It can be clearly audible through an open window or to neighbours, and its low-frequency hum travels further than fan hiss.

Fan speed and compressor load

Fan noise rises steeply with speed, so the difference between lowest and highest fan setting can be large. Inverter compressors speed up and slow down with demand: on a hot afternoon or just after switching on, the unit works hard and is loudest, then settles to a quieter level.

Fixed-speed units cycle on and off instead, producing a start-up surge and a noticeable change in sound each time — which some people find more disruptive at night than a steady hum.

Distance, walls and windows

Moving away from a portable unit lowers the level, but indoors reflections from walls and ceilings limit the benefit. A closed door between you and the unit usually helps more than a few extra metres in the same room.

Window and through-wall installations are weak points: gaps around a window kit can let both machine noise and outdoor traffic noise into the room. Sealing those gaps reduces both.

Continuous background sound and sleep

Steady AC sound raises the background level of the room. Some people find that this masks sudden noises such as traffic or barking; others find the hum itself disturbs their sleep. Masking does not reduce the total noise, so it is a trade-off rather than a fix.

For reference, WHO's 1999 Guidelines for Community Noise give 30 dB LAeq as a guideline value inside bedrooms, and its 2009 Night Noise Guidelines recommend 40 dB Lnight measured outside the home. A unit running in the 50s in a bedroom is well above those reference values.

Specifications versus what you measure

Manufacturer figures may be sound pressure measured at a defined distance in a test room, or sound power, which is a different quantity; outdoor units in particular are often given as sound power. Neither will match a reading taken at your bed or desk.

To compare settings in your own home, measure from the same spot with the same device, once with the unit off and once with it running at each fan speed. SnapRoomScore readings are uncalibrated estimates, so they are most useful for these relative comparisons rather than for checking a spec sheet.

Frequently asked questions

Related sound levels

Sources

• WHO — Guidelines for Community Noise (1999)
• WHO — Night Noise Guidelines for Europe (2009)

Exposure times follow NIOSH's occupational recommended exposure limit (85 dBA over 8 hours, 3 dB exchange rate). They are guidelines for limiting risk, not thresholds at which injury is certain.