2002 Mazda Protege Whirling/humming sound when driving

This is an odd sound which gets louder and faster as I speed up but only until about 55 MPH. At faster speeds the sound softens considerably but is still present. When loudest, the sounds cause slight vibrations. The oddest thing is that the sound completely disappears when I turn the wheel even slightly to the right only. This sound has slowly gotten worse. The front tires are close to needing replaced (they are 14 months old) but show no sign of uneven wear as far as I can tell and have decent tread left.