I had the same problem but at speeds of 40 plus MPH, I took it to the dealer, they said it was the transmission making that whistling, high pitched noise. Solution. New Transmission, under warranty, thank goodness.
Hardly a serious fault is it? What if you'd had a transmission or engine failure - what would you have done then?
Have the same car, a 2009 Santa Fe Limited, and the exact same problem from day one. Good car except for this hateful whistling noise at highway speed. Sounds like a dentist's drill and is very irritating; if driving into the wind, then it is loud enough to wake up our two year old daughter if she's asleep in the back.
After so many BS answers from the dealership, I have given up complaining about it. As for not buying from Hyundai again based on this, I would say yes... their customer service sucks and there is very little support; some of the reasons they tried to pass off for the noise were absolutely laughable... they should just admit that it is a design defect at least, as many customers have had the same problem. Just be honest with the customer, it would be more appreciated.
Ruined the experience of buying a new car for us...
Had a Hyundai before. Not a bad car, but not a great car either. And just like you, I discovered the customer service was not great and their vehicles have issues.
But what you haven't discovered yet, is trade in or resale value is real bad. It took me 6 months to sell mine private party, and that's after reducing my price several times. The local dealer didn't even want it... they had a sea of used Hyundais that they couldn't sell just sitting on the lot.
If you keep your car 5 to 10 years, I feel Hyundai isn't a bad choice, but if you tend to trade them in or sell them in a shorter period of time, your pocketbook is going to take a beating.