Hum and White noise

Hum noun - A monotonous sound like that of an insect in motion.

White noise and hum are semantically related In some cases you can replace phrase "White noise" with "Hum", this terms are similar.

White noise noun - A noise produced by a stimulus containing all of the audible frequencies of vibration.

Hum and white noise are semantically related in acoustical noise topic. You can use "Hum" instead a noun phrase "White noise".