Being that you have already been under the car with it running, I will not go into the safety aspects of that but to just say that you can never be TO SAFE! Use jack stands, and blocks of wood, and old wheels, and tree logs, and ...... well you can never have to much stuff piled under a car so that it does not fall and crush you when you are under it. Another very big thing to watch out for is rotating shafts and other moving parts so that you do not get yourself wrapped around a shaft and tear an arm or leg off. Now on to other things.
You may want to invest in a stethoscope to find where the noise is coming from. Link to scopes and info; even sound files to hear.
https://www.amazon.com/Lisle-52500-Mech ... B0002SQYSM
http://www.ebay.com/sch/items/?_nkw=ste ... rmvSB=true
http://www.enduringautomotive.com/autom ... ethoscope/
With the car up in the air and wheels running, making noise, you can use the stethoscope to locate where the noise is the loudest and where that location is at. This will help locate the part that is in question. On the internet, I can not hear it so I am guessing from what you have said and the first thing I would have guessed is the drivers side front wheel bearing. Any clicking sounds? That could be a bad CV joint on the drivers side. I once had a noise on our mini van that I would describe like you have, and not being 100% sure, I changed both front wheel bearings and the noise was still there. After doing more digging I found that the bearing where the drivers side axle goes into the trans-axle case was bad. I could move the inner CV joint and axle up and down, it was loose. There was also some leakage of transmission fluid from the seal. The other axle shaft was nice and tight where it went into the trans-axle case. I left it as I was not going to fix it on a van that had 160,000 miles on it and rusted out. About 6 months later the van got totaled out in a wreak so the problem went away. One way or another, nothing lasts for ever.
Good luck to you!