Engine Humming during idle and coasting
 

Just recently and also randomly my 2001 3.8L mustang has been making an unusual humming noise that I can hear inside the cab but not necessarily as loud from outside the car. It sounds like a muffled vacuum cleaner almost. I've been looking online and I've seen a lot of sites saying it's a failing fuel pump. I haven't had any work done recently. Most of my driving is done on the highway and my car hasn't had any mileage problems or problematic smells. Any help would be greatly appreciated it's annoying and if it's bad I want to take care of it before it gets worse (more expensive to fix). I'm on a small budget and hope it's nothing too expensive. Thanks so much