I’m trying to find a cheap used car that’ll only be driven for 2 years (Im in the military). I test drove a car today. It’s was a Nissan Teana. While idling, it was silent, but when driving, there was a low hum. However, it didn’t get louder with acceleration. It wasn’t the muffler, as I rolled down my window to check if it was coming from the outside. It was only audible inside the car. It seemed like it was just the rumble of the engine, but I wanted to come on here and make sure it was nothing too serious. TIA