echoing noise at 40-50 mph. kind of a humming and echoing noise coming from my left front. Could it be a hub bearing?

 

If you have access, try swapping the front wheels to see if the trouble shifts with the wheel.

My $2.00 program...
Try to isolate the problem.
Always trouble shoot as much as you can, rule out as many factors as possible.
If you have to bring it to a shop, you have some info. to give them to start off with.

Who knows what it could be without doing some invetigating.
Could possibly be a balancing issue.
Could possibly be an alignment issue.
Could be...
Narrow it down, pay for the cheapest possible 'fix' first.
Hopefully your problem is something simple to fix.
Good luck.