What would cause the extremely loud roaring ear deafening sound under front end on 1999 Ford Explorer

I have been told that there is a hole next to the catalytic convertor and that it will cost $1,800.00 to repair.
Supposedly the shop welded the hole but it is worse.
I have yet to take it elsewhere for second opinion.

The sound started very light now unbearable.

Please note:I replaced the muffler system in April.

Thank you for your assistance.

Asked by for the 1999 Ford Explorer
get a 2nd opinion.poss bad welding job
2 more answers , 3 more comments
Truck moving or standing still? Noise change with engine speed or vehicle speed?
Thank you everyone for your suggestions.

The answer was diagnosed by an additional two auto repair shops as "Front left wheel bearing needed replacing and the wheel was very dangerous and the bearings needed to be replaced.

How right they were!!!
It is humming along and I can actually think while driving and enjoy it too!!!

However, the third shop also showed me where the first "franchise" shop puttied up a hole in the pipe next to the catalytic converter area. There is a slight hum and I do know it will be extremely costly to repair. Plus struts are needed too. This explorer only has 83k on it.
Who did the muffler work, ask them to look at it, if they did something to cause your problem they should help you with that.
Thank you for your reply. A franchise company did the muffler work. The sound started lightly prior to the muffler work. That shop also diagnosed the hole prior to the muffler work.

The SUV also has little power. Going up a hill I will floor it & lucky to make it 20 mph. The shop said it needs a "tune up".($300.00? I remember when tune ups were lower than $100.)
If there is a hole next to the catalytic convertor, wouldn't that take the power out of the vehicle?
Have your fuel filter checked. The labor is close to that on the V-8, good thing it's not a 2005 or newer 5.4l.