Well, messing around with the sound mixer seems to have done it. Steps:
Opened PChat. No sound.
Opened volume mixer (right click audio speaker icon in system tray).
The only two things are the device (speaker/hp) and applications, under which only "system sounds" was showing.
Right clicked speaker icon, clicked "Sounds".
Got an error:
Windows has detected that audio enhancements for the following device are causing problems:
Speaker/HP (Realtek High Definition Audio)
Would you like to disable Driver Enhancements for this device?
Yes / No
I clicked yes, and the normal sound options window popped up. It didn't seem useful, so I closed it.
Now, as I recall, I did not have sound in CoH at this point.
I right clicked the audio speaker icon, clicked "Troubleshoot sound problems." It opened a window I thought would take some time, so I read Titan forums, clicked a link to a sea shanty, and made sure YouTube on chrome was playing properly (it was).
At this point, I decided to see if Chrome would show up in the "applications" section of the sound mixer. It did... along with "Name Not Available." Could this be CoH?
Apparently it was, because now I have sound.
However, the troubleshooting appears not to have finished. I now have a window open:
(https://i.imgur.com/klD3J7Q.png)
I clicked "cancel" and sound is still working, and Name Not Available is still in my sound mixer. So because I'm not entirely sure if I had sound immediately before the troubleshoot (after the disabling of driver enhancements) or after, I'm not sure what worked. I'm 75% certain I had no sound before the troubleshooting.