1996 engine hum

I have a 1996 that has developed a medium pitched hum during idol up to about 2000 rpm. It is noticeable both in and outside of the vehicle. Has anyone encountered this/have a solution?

Try this. Turn the car off. Wait a few seconds. Turn the innition on but do not start the car. If you hear the sound for just a second or two then it stops it is the fuel pump. I have a 98 that is doing the same thing. I was looking on this site to find out how to replace mine. Sometimes the hum stops. Then it comes bsck.
Good luck
Tom