The cross-load diagram is typical for a PSU with dedicated voltage regulation: the +12V voltage is ideal at any load distribution. The +3.3V voltage deflects by less than 3%. The +5V voltage exceeds a 3% deflection only at extreme loads. I can remind you that the industry standard allows a 5% deflection, so the Signature shows an excellent result in this test.
Output Voltage Ripple
It is all right on the +12V rail but the highest peaks of the pulsation on the +5V and +3.3V rails are higher than the allowable limit of 50 millivolts. The oscillogram does not show serious problems, though.
Take note of the difference in the pulsations on the low-voltage and +12V rails: it is because the latter is provided by the PSU’s main converter while the low-voltage rails have dedicated switching regulators working at a high frequency.
Fan Speed Control
The PSU is cooled by a D08A-12PS3-06AH1 fan from Nidec Beta SL. Nidec’s website does not mention that model, though. Despite the high wattage of the PSU, the fan measures 80x80x25mm only. It uses a 4-pin connection with PWM-based speed control which should provide a wide range of speeds.
Indeed, the fan speed varies more than threefold depending on the PSU load. At loads up to 400W it is rotating at about 700rpm, making the PSU absolutely silent. Then the speed begins to grow up in a linear manner, but the fan only becomes noisy at loads above 650W. Thus, this PSU is one of the quietest models available, especially at low loads.
It also means that a large fan is not a necessity for a PSU to be quiet. A clever approach to cooling system design is more important than size here.
I should note, however, that the PSU may be hotter in a system case with a top position of the PSU and poor ventilation. It then produces an audible hiss. Therefore you may prefer to use a system case where the power supply is installed at the bottom. This piece of advice refers to any PSU, though.