The rear wheel bearings on your car are responsible for taking the load off (literally) the rear axles and CV joints. It does this by providing a smooth, frictionless surface for the wheel to rotate on while the axles transfer power to the wheels. Over time, the bearings can fail from seal failure, faulty manufacturing, or normal wear and tear on your car. When this happens, you'll need to know how to troubleshoot the problem or you could end up damaging other, more expensive components on your car.
Drive your car around the block. Open the window on the driver's side and listen to the rear wheels.
Check for a metallic scraping sound. This is often somewhat akin to a whistling sound.
Increase and decrease speed and listen for the sound. If the sound increases in intensity or volume as vehicle speed increases or decreases, it is likely a worn, rough, or failing wheel bearing.
Shift the car out of drive and into neutral and listen for the whistling sound again, coming from the rear wheels. If the car is in neutral (the car is coasting) and the sound is persistent, the wheel bearings need to be checked and replaced.
