2001 GMC Sierra 2500HD 4x4 whine/whistle

At about 50mph, start to get a whine/whistle from right rear (sounds kind of like a jet engine). Noise gets higher/lower as speed increases/decreases. Just started 1-2 weeks ago, 145k miles. Intermittent, but 85-90% of the time. Help please. Thanks

Sounds like a bad right rear wheel bearing.