The team reduced the overall leaf blower noise by about two decibels, making the machine sound 37% quieter.

You omitted the most important data, it’s 2db overall, not 12db.

So your own “recalculation” isn’t even in the right ballpark as the correct answer.

Its people that misinterpret the information and perpetuate it like you are doing here that makes these look far better than they actually are.