If you want to claim that the fan the manufacturer used is too loud, you should also test at its max. operating temperature, not just in an air-conditioned office. Some equipment may be designed for high density rack-mount operation, requiring even more airflow. They may also try to keep the temperature down to reduce drift and noise.
There's a fairly strong correlation between air flow and noise for a constant fan size, so two fans of the same size that move the same amount of air tend to be fairly close in noise, at least for the common axial fans. Bearing noise can make a difference, especially if one of them has really bad bearings, but this tends to be fairly minor compared to the turbulence noise. The fan blades an also be adjusted to trade off pressure for air flow. Most of the fan replacements that decrease noise tend to boil down to decreasing air flow.
There's a quite good treatment of this topic on
SilentPCReview.com. They first try to choose more efficient components to lower the amount of heat they have to get rid of, decrease the impedance the fan sees so more air gets moved at the same speed, increase the internal temperature so the larger temperature gradient allows them to move more heat in the same volume of air, and the last thing is choosing a large, low speed fan with the least bearing noise. You'll also see is that the specs of many fans offered to retail customers tend to be flat-out wrong.
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