The car is a 2012 Toyota matrix. Starting to hear the noise a few month ago. Took to a mechanic yesterday diagnosed as suspension problem. Very interesting as it was just replaced four month ago. So we took it back to the mechanic who did the replacement. He couldn't tell if it's suspension or not.
The speed is most noticeable when driving at 100~110km/h
Attaching video of the noise here: https://imgur.com/a/2Pga5IW
It sounds like something loose, somewhere on the car, is flapping in the wind as you drive. The vibration sounds much too fast to be suspension-related as you drove on a smooth road in the video.
The best way to find this is to first check for anything loose under the hood that is catching the wind that enters through the front grille, such as the fan shroud or a similar plastic part. If nothing is found, then . . .
Place the car on a lift and start physically touching, bending and distorting various plastic parts under the car such as an engine shield, splash shields, air dams, mud guards, bumper skirts, wheel wells, and anything else that's made of flexible plastic. The mechanic should be looking for a part that is missing a fastener, which makes it loose and able to flap in a 100 km/h wind as you drive. A cracked part could also be loose and able to flap.
Let us know how this turns out!
