Just got the car back from the shop. They couldn't pinpoint where the noise is coming from because it disappears when the car is on the lift regardless of the speed.
So it must have something to do with the weight of the car when it's on the ground. Apparently after so many 8-shape road tests by the tech, the noise is inconsistent. (I didn't hear anything for a few miles after left the shop.) Before I took it to the shop, I would hear it every single time I hit around 30MPH.
They suspect it's either some debris stuck and it's coming loose now, or it's the wheel bearing but are not 100% sure. But the wheel bearing noise is usually a grinding or roaring sound, not a whining or whistling sound, right? I didn't want to spend $600 just to find out that it's not the wheel bearing.
So, I am back to square one.
If anyone else happens to figure it out, please post a reply.