2002 Toyota Corolla Replace Axle Bearings or more?

My wifes 2002 Corolla makes a humming noise starting at around 30mph and continues to make the noise until about 50 then the noise is gone till about 60 MPH I had a car service person look at it today and he is recommending that we replace the front axle bearings. Is this our best option or should we be considering replacing the front axles all together? The humming noise changes pitch when the steering wheel is turned from side to side. Thanks for your help!
Tristan