I've not seen any complaints of this and have not noticed it, so I don't know whether it's outside my hearing range.
If this is indeed a situation where they indeed all do it, it would probably require an engineering solution on Hyundai's part. The discussion in the Edmunds forum seems to be on point. I'd expect the radio and antenna shielding would be well-grounded, so any engineering fix would most likely involve some sort of in-line filter for the antenna cable.
Start with the dealer. Make them aware of the issue and have them check the vehicle. If they have difficulty repairing, they're likely to call technical assistance. If they believe it to be normal they're likely to take no further action. You'll want the dealer to call technical assistance in either case. If technical assistance tells them it's normal, there's nothing more the dealer will be able to do. Technical assistance may also propose a solution or report that one is coming but not ready yet.
If the above doesn't solve the problem, make a complaint to Hyundai consumer assistance. While making the complaint still won't guarantee a fix, it'll at least make sure Hyundai is aware of the problem. The more people that call with the problem, the more likely it is that the problem will be addressed.
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