This isn't a home improvement question, but one that applies to buying any product that makes noise or sound: how can you ask reviewers to compare the noise level of a product with some reference noise levels that are about the same across most people, places and situations?
An example to help explain my question better: I want to buy a window A/C unit. Every single one I see reviews for on Amazon has contradictory opinions across the decibel spectrum, from "It's quiet" to "It's so loud I have to crank up the TV".
Unlike with dimensions, the vast majority of people don't have a sound level meter. If they didn't have a ruler, you could ask them "How big is it in relation to a CD", since all CDs have the same diameter (12cm). What are some sound levels that are reliably about the same?
I've looked at this table of common decibel values, but ranges like "50 - 65" for normal conversation are way too imprecise, given that an increase of 10 db means a doubling of the perceived loudness and "every increase of 3 dB represents a doubling of sound intensity, or acoustic power". Also, the logarithmic nature of the decibel scale makes it too confusing to consider about asking random reviewers to think in any terms other than some common sound levels that are approximately the same everywhere (hence why I'm not posting this on Physics.SE).
- riffle-shuffling a deck of cards
- opening a soda can swiftly (though this is a short-duration noise and may be misleading when compare long-running appliances such as A/C units or refridgerators)
I realize that any sound will be perceived differently depending on the acoustics of the room but let's hope that reviewers can mentally map these "reference sounds" to the condition of the room they (and the appliance/product) are in. A soda can pop will sound much louder in a hardwood floor small room than in a larger carpeted room but when I think about that volume level, I think of it in the context of the room I'm in.