constant growl/hum in front?

i have a friend that has a 95 astro with all wheel drive. he is getting a sound that he thinks is coming from the front end. he said it seems to start once you get up past 8 or 10 mph. then it seems to change with vehicle speed. has anyone else had this problem or have helpful info. thanks, luke.

They are known for worn idler arms which can cause excessive tire noise also a sticking hub can cause noise being out of alignment and low on powersterring fluid or with a worn powersterring pump can make exsissive noise.
Hard to diagnose a noise without hearring it though.