A bedroom air purifier is useless if it's too loud to sleep with. But "quiet" is subjective, and manufacturers aren't always honest about noise. Here's how to find a purifier you can actually live with.
Understanding Decibels
Noise is measured in decibels (dB). The scale is logarithmic—every 10 dB increase sounds roughly twice as loud.
| Decibel Level | Comparable Sound | Bedroom Suitable? |
|---|---|---|
| 20-25 dB | Whisper, rustling leaves | Excellent |
| 25-30 dB | Quiet room, soft whisper | Very good |
| 30-35 dB | Library, quiet office | Good for most |
| 35-40 dB | Quiet conversation | May bother light sleepers |
| 40-45 dB | Refrigerator hum | Noticeable, some adjust |
| 45-50 dB | Normal conversation | Distracting for sleep |
| 50+ dB | Background music, AC | Too loud for most |
The Speed-Noise Tradeoff
Air purifiers are quieter at lower speeds but clean less effectively. This creates a tradeoff:
- Low speed: Quiet but lower CADR, slower cleaning
- Medium speed: Moderate noise, reasonable cleaning
- High speed: Loudest but fastest cleaning
The Sleep Mode Trap
"Sleep mode" or "silent mode" often runs at very low speeds with minimal airflow. Great for noise, less great for actually cleaning air. Some units drop to near-useless CADR in sleep mode.
Better Approach
Look for a purifier with acceptable noise at medium speed, where it still delivers meaningful CADR. This gives you both effective cleaning and tolerable noise.
What to Look For
Low-Speed Noise Under 35 dB
For sleep, you want the lowest speed to be under 35 dB. Under 30 dB is excellent.
Acceptable Medium-Speed Noise
Medium speed should be under 45 dB for bedroom use. This is where you get meaningful air cleaning without sleep disruption.
Size Up for Quiet Operation
A larger purifier can run at lower speeds while delivering the same CADR as a smaller unit at high speed. Oversizing slightly allows quieter operation.
Noise Characteristics Matter
Not all noise is equally disruptive:
White Noise (Fan Sound)
Consistent, steady airflow sound. Many people find this soothing and sleep better with it. It can mask other environmental noises.
Mechanical Noise
Rattling, humming motors, or vibrations. More annoying than pure airflow sound. Can indicate quality issues.
Intermittent Noise
Some "smart" purifiers adjust speed automatically. Sudden changes in noise level can be more disruptive than constant sound.
The White Noise Benefit
Some people who initially worried about purifier noise end up preferring it. The steady fan sound masks outside traffic, neighbors, and other disturbances. If you already use a white noise machine, a purifier might replace it.
Practical Tips
- Read reviews specifically about noise—specs can be optimistic
- Position away from your head—even a few feet makes a difference
- Give yourself an adjustment period—new sounds seem louder at first
- Run on higher speed before bed—then turn down when sleeping
- Check for vibration—floor contact can amplify noise