Fan noise
The total acoustic power emitted, independent of distance. ISO 21118 asks for this in bels.
- Unit
- B (bels)
- Standard
- ISO 7779:2018 / ECMA-74; ISO 9296 declared values
- ISO 21118
- ISO 21118 optional
- Better
- ↓ Lower
Fan noise on a dB(A) scale from the hearing threshold (0) to a vacuum cleaner (85). Eco 26 dB(A) at 1.0 m, about 16.5 dB(A) at 3.0 m; Standard 30 dB(A) at 1.0 m, about 20.5 dB(A) at 3.0 m; Boost 36 dB(A) at 1.0 m, about 26.5 dB(A) at 3.0 m. In a free field the level drops 6 dB each time the distance doubles.
Reference sounds are approximate ranges from the Wikipedia 'Sound pressure' table of examples. Default projector figures are illustrative, not a specific model. Distance falloff assumes a point source in a free field (outdoors); in a real room reflections keep levels higher at distance, and dB(A) hides low-frequency hum and tonal whine.
- Change vs 1.0 m
- -9.5 dB−6.0 dB per doubling
- Eco at 3.0 m
- 16.5 dB(A)26.0 dB(A) rated
- Standard at 3.0 m
- 20.5 dB(A)30.0 dB(A) rated
- Boost at 3.0 m
- 26.5 dB(A)36.0 dB(A) rated
Show the numbers
| Formula | L₂ = L₁ − 20·log₁₀(d₂ ÷ d₁) |
|---|---|
| Eco at 3.0 m | 16.46 dB(A) |
| Standard at 3.0 m | 20.46 dB(A) |
| Boost at 3.0 m | 26.46 dB(A) |
How to compare it
Sound power level(B (bels))
The more rigorous metric, but rarely published by consumer brands.
Measured noise(dB(A))
Measured fan noise per mode at a stated distance.
Paired with our recorded audio clips so people can actually hear it.
Standard: Reviewer SPL meter (distance, weighting recorded)
Deep cut
Sound power level. 1 B = 10 dB. Sound power (L_WA) is not sound pressure (L_pA). Pressure depends on distance and room, while power is a property of the source. ISO 9296 declared values (L_WA,d) include a statistical adder.