Every guide on this site ranks products by the noise figures their makers publish. And almost every guide carries the same warning: be careful comparing one brand's figure with another's. This page explains why, with real examples from the products we have checked, and shows the few comparisons that do hold up.
We do not measure anything ourselves. Every example here comes from a manufacturer's own page or manual, or from a government source, and we name it.
One blower, four numbers
Start with the clearest example we found. Husqvarna's manual for its 125B leaf blower lists four noise figures for the same machine:
- 93 dB(A), the sound pressure at the operator's ear, measured to ISO 22868
- 71 dB(A), the sound pressure at a bystander's ear, measured to ANSI B175.2
- 106 dB(A), the sound power level, as measured
- 110 dB(A), the sound power level Husqvarna guarantees
None of these is wrong. Each answers a different question: how loud is it for the person holding it, for a neighbor, or in total. But if one maker prints the 71 and another prints the 93, the second blower looks far louder even if it is identical.
That is the core problem. A decibel figure means nothing on its own. It needs to say what was measured, where, and how.
What a figure should tell you, and usually does not
A comparable noise figure answers four questions. Most published figures answer one or none.
1. Which setting?
Most appliances have more than one speed, and the quietest speed can be twenty or more decibels below the loudest.
- Blueair lists its Blue Pure 411i Max at 19 dB on low and 46 dB on high. That is a 27 dB spread in one product.
- Winix lists its L201 humidifier at 30 dB at its highest speed.
- Many makers give a single number and do not say which setting it describes.
So Winix's 30 dB, which describes the loudest setting, may be quieter in use than another maker's 24 dB that describes the quietest. Without the setting, you cannot tell.
2. How far away?
Sound gets quieter as you move away from it, so a figure measured close to a machine reads higher than one taken farther away. OSHA notes that indoors, sound falls off less with distance than it does in open space, because rooms reflect it.
Very few makers state a distance. In our research:
- Levoit says its Superior Studio humidifier's 19 to 45 dB was measured 1.5 m from the unit.
- Campbell Hausfeld lists one quiet compressor at 68 dBA at 3 ft.
- Milwaukee rates its M18 FUEL blower at 54 dB(A) at 50 feet.
Of sixteen air compressors we checked, Campbell Hausfeld was the only maker to state a distance. So a compressor listed at 60 dB is not necessarily quieter than its 68 dBA at 3 ft.
3. Sound pressure or sound power?
Most figures are sound pressure: what a microphone picks up at one spot. Some, often on European spec sheets, are sound power: the total sound a machine gives off, wherever you stand. Sound power figures tend to be much higher numbers. Husqvarna's 110 dB(A) sound power and its 71 dB(A) bystander figure describe the same blower.
Liebherr's wine fridges show the European style: a figure "according to EN 60704-3", the method behind European energy labels. It is useful, but it cannot be set beside another maker's bare number.
4. Which standard?
A standard fixes all of the above: setting, distance, room and equipment. When two makers use the same standard, their figures can be compared. Some standards we have seen cited:
- ANSI B175.2 for leaf blowers, measured at 50 feet
- ISO 22868 for sound at the operator's ear on outdoor power tools
- EN 60704-3 for household appliance noise in Europe
But most makers name no standard at all. Of eighteen wine fridges we checked, only Liebherr named one.
Signs a figure is soft
Some figures come with warning signs built in.
A ceiling, not a number. "Under 38 dBA" or "less than 41 dB" tells you the maker's figure is below a line, not what it is.
"As low as". A figure described as "as low as 26 dB" is the quietest setting, by definition.
A bare range. "20 to 40 dB" with no labels leaves you to guess which end is which.
Two figures on one page. Summit's page for one wine fridge gives 32.4 dB in its spec table and 32.2 dB in its feature text. Makers sometimes disagree with themselves.
dB with no A. A-weighted figures, written dBA or dB(A), are adjusted to match how people hear. Plain dB leaves that unstated. See dBA explained for more.
The comparisons that do work
It is not hopeless. Some comparisons hold up well.
Figures measured to the same standard. Leaf blowers are the best example. STIHL, Milwaukee, Makita and ECHO publish figures under ANSI B175.2, the 50 foot bystander method, so those numbers line up. Cities rely on this too. Portland, Oregon keeps a list of leaf blowers at 65 dBA or quieter at 50 feet, certified using ANSI methodology.
Certified sone ratings. Bathroom fans and range hoods are rated in sones, and the Home Ventilating Institute certifies fan ratings. See sones vs decibels.
Figures within one brand. A maker probably measures its own range the same way, so its figures show the steps between models. Bosch, for example, lists its dishwashers at 48, 44 and 42 dBA as the price rises.
The same setting across brands. If two makers both label a figure as the low speed, or both as the highest speed, the comparison is fairer, though still not exact.
How we handle this in our guides
In every guide, we quote each noise figure in the maker's own words, with any setting, distance or standard they give. Where the maker gives none, we say "basis not stated". We rank on published figures, but we treat small gaps between brands as uncertain, and we say so. Where a category has a shared standard, like leaf blowers, we rank only on that.
A quick checklist
Before you trust a gap between two noise figures, ask:
- Do both describe the same setting?
- Do both give a distance, and is it the same?
- Are both sound pressure, or both sound power?
- Do both name the same standard?
- Is the figure a real number, or "under" or "as low as"?
If the answer to most of these is "not stated", treat a gap of a few decibels as no gap at all. To decide what level to aim for, see how quiet is quiet enough, room by room.
Common questions
Can I compare dB ratings between two brands?
Only when both makers tell you the same things: the setting, the distance and the standard. That is rare. Most makers print a bare number, so a gap of a few decibels between brands may not exist at all. Compare within one brand, or on a shared standard such as the ANSI 50 ft rating for leaf blowers.
Why does one product have several noise figures?
Because each describes something different. Husqvarna's 125B manual lists 93 dB(A) at the operator's ear, 71 dB(A) for a bystander under ANSI B175.2, and a sound power level of 106 dB(A) measured and 110 dB(A) guaranteed. All four describe the same blower.
What is the difference between sound pressure and sound power?
Sound pressure is what a microphone picks up at a particular spot, so it depends on distance and the room. Sound power describes how much sound the machine gives off in total, wherever you stand. Sound power figures tend to be much higher numbers, so never compare one against a sound pressure figure.
Which noise ratings can I trust to compare?
Ratings measured to a shared method. Leaf blower figures at 50 feet under ANSI B175.2 are one example, and cities such as Portland write their rules around them. Certified sone ratings for bathroom fans are another. Within one brand, figures are also safer to compare, since the maker likely measures its own range the same way.
Does dB mean the same as dBA?
No. dBA, or dB(A), is A-weighted to match how people hear. A maker that writes plain dB has not told you whether it weighted the figure. Some makers use both forms on the same page, so do not read too much into the label alone.
What does "under 38 dB" mean on a spec sheet?
It is a ceiling, not a measurement. The maker is saying its figure is below 38, without giving the figure. Treat "under 38" and "38" as roughly the same, and do not rank a product above another on that wording alone.
