car making a humming noise at 25 mph?

And increases in loudness with more speed, slight vibration in gas peddle, non in the brake, don't feel any change when turning right or left, suspect left side though..... have old tires, and need a serpentine belt replacement,

Sound is kinda like a small airplane propeller

Any idea on what it is

.. engine doles quite, tranny. Shifts smooth

jon_mac_usa_0072014-04-10T21:56:48Z

Probably a bad wheel bearing.