Elsewhere they say “15 dBa quieter” than an equivalent helicopter - I am not very good on dB - is that consistent with “100x quieter” ?
For power (not voltage) the conversion from decibels (dB) to linear is y = 10^(x/10) where x is the value in dB. Thus for x = 15dB then y = 31.6. So, no, not even close to "100x quieter".
To go from linear to decibels when measuring power the equation is x (in dB) = 10log(y).
Still worse is that because of the way humans (not machines) perceive sound, each factor of 10 equates to twice as loud or half as loud, depending on which direction the calculation is going. Hence something that is a factor of 10 (10dB) less is half as loud (2 times quieter), and a factor of 100 (20dB) less is a quarter loud (4 times quieter). Thus if this wonderful aircraft is 15dB quieter than a helicopter it is somewhere around 3 times quieter as the human ear perceives things. So very much not even close to "100x quieter"!
Then there is the subtlety of the fact that they use the sound pressure level "A weighted" scale. That's where the "a" on "dBa" comes in. But at this point it's not worth quibbling about how much crazier their numbers are
