My 2019 Sportage makes a faint pulsating, thumping noise from "somewhere" clearly audible at around 40mph on a very smooth road surface. It's not noticeable at higher speeds or at very low speeds. Tires are OEM at 25000 miles and the noise synchs with the RPM of the wheels. No vibrations are evident, wheels are balanced, and tires look good with a visible check. Anyone experience this or have any ideas? How can I isolate the cause? Thanks.