Is this normal? Yes and no. Dare I say it, you may be overly sensitive to the normal resonant sound of electrical devices. All electrical devices may, or may not create 60 Hz hum during operation, depending on who's listening... You are obviously not an electrician, and haven't dealt with the exact same question you are asking time and time again. A slight hum from a lamp, can sent some into a frenzy. Is it normal? Yes, and no depending on the degree, and how much money you would like to spend for some of the corrective measures. There are some, and everyone else but you will not be able to hear it possibly. Some hums are normal, some are not. All motors, lamps, transformers hum to a varying degree. Some electrical appliances emit noise as well. The average TV set can be heard by a dog for 100 yards in a state that a human would consider silent. Ultra-sonic motion sensors of certain Db levels are illegal in some states. For instance, I have neighbor down the road with motion sensors for his alarm system that make a dog whistle noise as you walk by, the person who lives there is totaly deaf to that frequency, thinks people are crazy when they tell himabout it.
I suggest you get a second opinion from someone (an electrician) who can actually hear it. As we could not quantify what is normal, or not.
