No sound in Firefox

[Marc Shapiro <marcnshap@gmail.com>]

I recently upgraded my Firefox to v52 and immediately lost all sound in 
Firefox.  Apparently Firefox now requires PulseAudio, which I had 
previously uninstalled due to issues which I no longer remember.  I 
tried installing PulseAudio, but still no sound in Firefox.  Also, no 
sound anywhere else.  I uninstalled PulseAudio and sound came back 
(except for Firefox).  I reverted Firefox to v51.0.1 and I have sound 
everywhere.

I would like to reinstall PulseAudio so that I can upgrade Firefox, but 
I can't get it to work.  Can anyone help me get sound working with 
PulseAudio?


Marc