On Nov 3, 2:21*pm, DerbyDad03 wrote:
I have a Goodman 90+ furnace with a 3" PVC output pipe, which ends in
vertical T.

Here's a side view, with W being the wall:

W
W * * * |
W-------|
W * * * |
W

I've always thought that it makes more noise than it should when the
furnace is on. It's sounds like a steam pipe at a factory.

If I were to compare it to anything, I'd say it is 3 - 4 times louder
than my AC compressor.

Is that normal?

Mine is noisy, but I had no need to quiet it. Resonances can make
things worse,
and sharp exit point will make it worse. You can put a muffler on it.
Why vertical T ?
Odd thing people do. Put your hand over the top exit and see if
it improves sound. A muffler is made with a larger pipe, preferably
with a bend, with a lining of fiberglass
around the perimeter then a reduction in pipe size. You want the exit
to be smaller
than the main pipe size. You have TWICE the exit size as your main
pipe.