Oh boy, you're in the world of audio sound issues 
This is a pretty good read and discusses both your buzzing and humming:
--
The Rugged Motor Driver: two H-bridges, more power than an L298, fully protected
Oh boy, you're in the world of audio sound issues This is a pretty good read and discusses both your buzzing and humming:
--
The Rugged Motor Driver: two H-bridges, more power than an L298, fully protected