No. It was not "above" the noise floor. Sound is additive, it's like wattage.
Here's a voltage example to illustrate how batshit crazy the DF measurement is:
Floor : 2.8V
Signal : 0.4V
With cheap multimeter without decimals, I get either 2V or 3V floor and 3V signal, when the actual signal was 0.4V.
Yes it was. The noise floor can be one of two things. The lower limit of sensitivity for the measure device or the actual lower limit based on ambient noise levels.
Yes it is additive. But if a source is significantly lower than ambient noise and/or measuring device sensititivy, then it will have a negligible effect.
In the DF measurements that is quite evident. You have to basically get right on top of the XO to be able to differentiate it from the ambient noise and/or get enough of a reading to register on their measuring device. For the PS4 at those distances the effect is very pronounced but once you get to 3 meters the impact is insignificant unless gaming.
Also note that the measured sound pressure levels of the PS3 when gaming at 3 meters is roughly equivalent to the Xbox One when gaming at 1 meter. This would not happen at all if the PS4 and XO in the DF analysis had the same sound characteristics as ones used in the Heisse analysis. While it is quite probabe that the XO is roughly equivalent in both, the PS4 that DF used on the other hand is significantly louder than the one Heisse used.
Anyway you look at it, while quiet, the PS4 is still significantly louder than the XO in the DF review. And subjectively louder in just about all review sites that have compared the two which is exactly what you would expect going by the DF analysis.
Still, that says absolutely nothing about how noisy/quiet the PS4 will appear to be depending on the ambient noise levels of any particular persons game room combined with how sensitive they are to differences in noise levels (changes in sound pressure).
In many people's relatively noise living rooms, I fully expect that the subjective and relative noise experience with a PS4 will be quite good as the DF comparison shows.
I imagine most people won't be bothered by it (assuming ambient noise from consumer electronics bothers them in the first place) until you get it into quieter environments.
Regards,
SB