The noise seems to come from rear.

The tone and loudness are directly proportional to car speed.

It does not seem to be engine noise. I can change engine rev from 2000 to 1500 quickly by releasing gas pedal. But the tone of that noise remains almost the same.

This noise is also present while I am gently braking from high speed. The tone becomes lower with decreasing car speed.

The noise does not change its tone suddenly at tranny gear upshift.

There is no annoying vibration of seat with the noise.

It is somewhat hard to tell tone of noise, but, at about 50 mph, that noise seems to have definitely higher tone than what people usually call 'hum'.




I included a video below of me pulling out
https://streamable.com/1lxvql

Is the noise louder when cornering in a particular direction?

The rear axle bearings failing are quite noisy.
Not a fun job to change either.
It could also be the center driveshaft support bearing.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!