Mitsubishi Repair: 98 lancer glxi auto, exhaust piping, loud noise

Question
ive been hearing a sound(like from a muffler with a hole in it)i tot before it came from it but it doesn't.its loud that even i have windows closed im hearing it.it sounds only wen im accelerating at about 40 kph the faster i get the louder the sound. its very noticeable when you are driving downhill with neutral. i dont know where it comes from. but it seems it doesnt come from the tires or wheel based. all nessesary fluids,oil are in normal level. any idea what could be it?

Answer
Stephen,
You may want to have your entire exhaust system checked out by a mechanic.  There could be a leak anywhere in your exhaust system, and that would cause the noises you are hearing.  Your catalytic converter may have malfunctioning, and that can cause the loud noise you hear.  Have it thoroughly inspected and patch any holes that are found.  If a leak is severe enough, you may need a new section of exhaust piping or exhaust component.
Good luck!