Christian, thanks. It is a 20% reduction which I agree would be very
noticeable.

It isn't a 20% reduction. The different between 52 and 43 is the same as the
difference between 10 and 1. It is even the same as reducing 5 to -4. It is
reducing the power of the noise by a factor of 8. Ears have an amazing
dynamic range, so it won't actually be perceived as an 8 times reduction. I
would guess it will sound about half as loud.

Christian.