We have a gradually louder noise happening when accelerating beyond the in park position, so when stepping on gas pedal you can hear it;louder in second gear but volume tapers off when in 4rth/drive to passing/highway speeds.
Its seems to be also a vibration that is under car in center area, maybe at catalytic converter ?
Not sure....heat shield , exhaust hanger broke ?
any ideas ?

 

buzz? Rattle? Hum? Roar? Moan? Online car diagnosis is good for the vocabulary.

 

the sound is variable with engine speed, but mostly like a buzz with a rattle , as it sounds like a loose part that is vibrating or shaking against another part, the hum or buzz like sound changes with a rattle sound then as car is at highway speed, it tapers off.

 

u check the heat shields behind the turbo?

 

oh mine is a non-turbo...but the local midas muffler guy guy I trust took it for a drive, put it on the lift, and had a second man step on gas pedal to seek the noise; it cam from inside catalytic converter, now I got to choose an aftermarket to be welded on, or some other alternative pipe work...?

 

Here's the thing - the factory part is a single unit that includes the flex pipe and the cat. Its not cheap ($400) but the risk of welding in a replacement cat is that you may still wind up replacing the flex pipe soon enough (a common point of failure - more so than the cat). You will also want to consider replacing the O2 sensors while the pipe is out as well.