The key is determining when the noise changes—not just how fast you're driving. Several different components can produce a whining or humming noise, but each has its own pattern. That's why proper diagnosis is so important.
Transmission Noise
A transmission-related whine often changes with:
Gear selection
Engine load
Acceleration or deceleration
Torque converter engagement
For example, if the noise changes when the transmission shifts gears or disappears when the torque converter locks, the transmission becomes a strong suspect.
Wheel Bearing Noise
A worn wheel bearing usually changes with vehicle speed, regardless of engine RPM.
One of the biggest clues is what happens while turning:
If the noise gets louder during a left turn, the right wheel bearing is often carrying more load.
If it gets louder during a right turn, the left bearing may be the culprit.
Wheel bearing noises typically don't change because the transmission shifts.