What power conditioner will help in my situation?

Personally, I don't think a power conditioner will fix that problem.
Is there no other circuit you can use even if it means running an extension cord from a different outlet in a different room?

Larry's advice is very good, see if you can put it on another circuit, that would be your cheapest fix. If not, a dedicated line would be your second cheapest option. If you cannot do that, you could try buying a power conditioner that uses isolation transformers, like Equi=Tech.

Yes, I agree that trying a long extension cord running to a different room should be the first thing that you should do, at least as an experiment.

But can you clarify what you mean when you say "when I change the fan speed there is a low frequency hum when I turn the fan speed from low to medium etc." Does that mean that the hum occurs only while you are changing the fan speed, and perhaps for a second or so afterwards? Or does it mean that the hum is always present, but is affected in some manner by a change of fan speed? Or does it mean that the hum is not present in "low," but is present at the faster settings?

Regards,
-- Al

PSAUDIO P10 works well for me with the same problem

I'm glad I have user adjustable electronic switch board with more dosens of combos how to customize outlets and power.