Driveline noise between 20 - 45 mph

[Greg Fine]

Hi All,  I have a 2015 Suburban LT 2wd with around 100k on it.  Recently it began making what sounds like a bearing hum between 20 - 45 mph.  However, it’s not a consistent hum as it gets louder and softer at different points in the revolution (almost like a whirling noise of sorts).  The first mechanic I went to said couldn’t be bearing bc it wasn’t a consistent sound.  We thought it was coming from the front so mechanic recommend changing out the pads and when that didn’t work the rotors as well.  Unfortunately this didn’t work so we took it to another mechanic whom thought the sound was coming from the rear and recommended we change out the emergency brake shoes so we changed that at the same time I had a transmission fluid and filter change.   Runs great other than this but we are at a loss and really don’t want to deal with mechanics just guessing.  Anyone have anything similar or thoughts?  Thanks in advance!