Hey OP,
The reason a transformer hums has to do with the quality of the AC, and it's internal construction. DC on the line, caused by too much draw from the positive or negative AC power is the usual suspect, as are manufacturing deficiencies in construction.
You can read about this in much more detail here:
https://testguy.net/content/259-Transformer-Humming-Noise-Explained
But the point is, the orientation of the transformer in regards to the earth is not what causes it, nor is the chasis design. Mechanical hum is a matter of the transformer, and incoming power. Now, it is certainly possible that hum may be louder in one orientation than another. :)
The reason a transformer hums has to do with the quality of the AC, and it's internal construction. DC on the line, caused by too much draw from the positive or negative AC power is the usual suspect, as are manufacturing deficiencies in construction.
You can read about this in much more detail here:
https://testguy.net/content/259-Transformer-Humming-Noise-Explained
But the point is, the orientation of the transformer in regards to the earth is not what causes it, nor is the chasis design. Mechanical hum is a matter of the transformer, and incoming power. Now, it is certainly possible that hum may be louder in one orientation than another. :)