A noise or vibration that is engine speed dependent is usually associated with the driveline, while a similar problem that occurs at a particular road speed is more often a problem with a wheel or suspension component. The main exception to that is the differential which is part of the driveline but determines the vehicle’s speed, so can contribute a speed-dependent noise or vibration, too.Beyond that, you could be looking at a fault with a wheel bearing, a deformed tyre, bent rim, worn suspension bush, bent axle or suspension arm or pretty much anything else. A rolling-road dynamometer (kind of like a treadmill for cars) might be one way of achieving the problem speed while a mechanic looks and listens on.