No doubt for very sound reasons, the heated bed on my Prusa i3 is supported on three not-very-well-separated linear bearings. This set-up has a harmonic frequency that gets triggered at various points as the bed is moved in the Y-axis. The result is an intermittent buzz/hum that is expressed in the object being printed.

A pair of these 'things' are clipped onto the rear on my bed and rest on the Y-axis rails (notched side to rail). The result is a significant reduction in the buzz/hum, and thus an improvement in the quality of my prints.

Note that installing a pair of these 'things' could impact the full range of your Y-axis.