Thanks for the replies.

@Cruiser: I remember the thread well. I checked that one before I set this one. I even posted there that I didn't have such noise. Which is partly true as my noise is not that kind of whistling or whining. It's continuous low frequency, I'd compare to a subwoofer doing 100Hz.

@NXMX5: It doesn't change. It depends on cruising speed not the load. It's the same noise within the range of 60 to 70mph.

Tomorrow I'll check the tire pressure and listen to it again carefully.

Thank you guys.