469
Students’ Leaf Blower Suppressor To Hit Retail
(hackaday.com)
This is a most excellent place for technology news and articles.
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.