Decibels aren't additive, they're logarithmic, so this makes no sense at all.
You can't add or remove a component and say it adds or removes 14 dB under all conditions. An addition of 14 dB means you're multiplying the total sound energy by about 3.75 times.
It might add or remove 14 dB on ground with no engines running, but in flight it probably doesn't change measured dB level at all. If the thing adds 14 dB in flight, it would be like putting a third engine in your lap.