"Several decibels" means a few units of measurement that are used to describe how loud or quiet a sound is.
Full definition
The Bolt II's idle performance also beats the Origin Genesis and CyberPower Zeus Mini
by several decibels.
That's over ten decibels louder than the quietest Skylake desktop we've reviewed, the Origin Millennium, and
several decibels noisier than other recently tested rigs.
When it does, it's noticeably louder by
a several decibels.