2001 Honda civic lx humming noise - wheel bearing or transmission (bearing) issue?

2001 Honda civic lx humming noise - wheel bearing or transmission (bearing) issue?

Added (1). The car has about 145000 miles. The noise usually is observable above 20mph and appears to be a humming noise. The dealer seems to think its a wheel bearing or/and hub ($375-$500). An independent mechanic who test drove and inspected by raising it on the lift and a stethoscope like device thinks the noise might be related to transmission and suggested a transmission fluid flush. I think I had neglected to change/add transmission fluid at 120k as the manual recommended. How best to identify issue?

On a road with very little traffic around, drive the car up to whatever speed the noise is most easily heard from inside the car. Then shift from D to N and coast in neutral for a few seconds while listening for the noise.

If the noise is still audible with the shifter in 'N', then I'd rule out that the sound is being produced by the transmission.

If the sound disappears when you put the transmission in Neutral, then can be heard again once you shift back into Drive (you can safely shift back into D from N while you're coasting BTW, just leave your foot off the gas when you do it…), then the sound is probably coming from something in the transmission and not the bearing/hub.

Do NOT do transmission flush! If you really want to risk ruining your tranny, the flush is a good way to do it. The fact he recommended a flush on your car (especially at over 75,000 miles) tells me that you should stay away from that mechanic. He wants your money. Flushes really aren't good on newer cars either, but on a car with 120K on the odometer? That's just mad!