If you are buying , look for dBA (A-weighted decibels). The "A" weighting adjusts the raw dB measurement to mimic the human ear's frequency response. This is the standard for safety and industrial equipment.
Here is a quick reference chart for common household appliance levels: sones vs db
where P1 and P2 are the sound pressure levels being compared. If you are buying , look for dBA (A-weighted decibels)