Maybe it isn't mechanical .... if it sounds the loudest sitting in the driver's seat, check the firewall and see if there is a ripped grommet or seal or simply an opening that is allowing normal engine noise to reach the cabin.

Haasman

__________________
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)