I've got a 96 Civic with automatic trans and 130k, and a noise which seems to come from the front left side and increases with speed, not rpm. It sounds very much like a bearing and makes a low-pitched howling noise which just keeps getting louder the faster you go. It doesn't change when swerving left or right, and doesn't change when the trans is put in neutral.
I immediately assumed it was the wheel bearing, but the noise is unchanged after replacing the driver's side bearing.

Any suggestions? My mechanic thinks it might be a bearing inside the trans which connects to the CV shaft. Is that a common thing to go bad, and how much should it cost to replace?

 

if your mechanic couldn't tell then you need a new one. jack up the front of the car hold one wheel still drive up to 40-50mph stop hold the other side and repeat. that bearing the connects to the CV shaft would be the diff bearing a stethascope works good for finding noise's in the drivetrain.