Hum, buzz sound

I purchased a used 2003 Jeep Liberty Limited yesterday w/ 93,000 miles and hadn't noticed this sound until today..for all I know it's normal but want to see if others know what it is.
I only hear it when it is quiet, no radio on or fan blowing.

When I put it in reverse or drive only, it makes this groan/motorized sound..
Normal, not normal?...Any ideas?

I looked around online and sounds like it is normal if anyone reads this later and wonders.

If it buzzes for 1 -2 seconds when you put it in gear, that's normal.