I'm hearing a high pitched wah-wah-wah-wah sound when I'm decelerating, which is most noticeable at low speeds (e.g. when slowing down from 20 mph to a stop). Is this a noise a failing torque converter would make?

 

If it is the propeller shaft, it can sound like a whine, kettle whistle, or a squeal (rubber to metal). If you have your windows down, it will sound like it's from the passenger front side although it is right in the middle.
Normally it starts above 80kmh but you will hear it at lower speeds the worse it gets.
Pretty much a one hour job to get it replaced.

 

It's hard to tell exactly where it is coming from. It is very subtle, yet noticeable. It isn't a scraping or squealing noise. It kind of sounds like the noise a jet engine makes when it is shut off, but with a sinusoidal pattern to it. It is present at all speeds, but barely perceivable likely due to road noise, which is why I can hear it most when coming to a stop.

 

...it has a sinusoidal pattern to it at lower speeds and decreases in frequency as I come to a stop, so carrier bearing is a good possibility. I'll jack it up this weekend and take a look.