Listening to some of the videos the noise is very common with hydraulic systems running gear pumps both electrically driven pumps and engine driven. Reading the specifications from an earlier post, the pump is a brushless DC motor, likely with digital control, and a gear hydraulic pump. These pumps will be operating at near full relief pressure and can produce the most noise during steering cycle while the car is moving at its slowest and will go into bypass, over relief or electronically controlled pump derate at full lock. The pressure required to operate the power steer and noise will decrease controlled electronically as the car increases speed and require less steering assistance. Nearly every engine belt driven power steer system in cars use a vane type pump with a directly mounted reservoir which is generally quieter then a gear pump and a remote reservoir . There will be tolerances in the pump and the relief valving and the steer box valving so there is going to be some variance in pressures from vehicle to vehicle. A slight pressure variance in a hydraulic system from relief and bypass adjustments can be enough to increase pump or valve noise. Being a simple vehicle power steer system these valves will be non adjustable and likely to be very basic in design ie not temperature compensated or pilot controlled. Other areas the pump causing excessive pump noise is reservoir level too low, air being pulled in on the pump through the suction hose or reservoir joints due bad or lose connection, excessive turbulence in the reservoir from returning oil especially with low oil or and in some instances not enough reservoir pressure to maintain good pump fluid delivery under some operating conditions.