A 20" Lasko box fan is about as cheap as they come - and, consequently, noisy and inefficient. The thing retails for $20, the budget for quieting measures is $0. In particular, especially when placed at a window (where it's expected to generate a pressure differential) you get a counterflow effect in the corners, and the 5 blades create individual pressure pulses as they move near to the 4 flat sides of the enclosure and then out into open air.

A quality high-volume, low-speed industrial drum or axial HVAC wall fan costs a whole lot more than $20 but the quiet, low-frequency noise is so much less intrusive.

Another mechanism (if you don't want a 36", 1/2 HP galvanized industrial contraption on your desk) is to concentrate the airflow near the user. Less power, but more concentrated. I've got a big fan that helps in the morning and evening to exchange air through the entire house, but on my desk I've got the biggest PC case fan I could find (a 230mm monster) wired to a speed controller cable and then directly to a 12V wall wart. At ~300 RPM, you can almost keep up with the motion of a single blade with your eyes, at 500 or 800 RPM it's barely perceptible... but it's only about 8x8x1" and keeps the air moving over your skin!

Ceiling fans are silent or nearly so in my experience and work a lot better than separate fan units imo.