I just installed Audacity to make a quick edit on an a MP3 file. I installed 2.1.2 from the default Linux Mint 18 repo, opened Audacity and selected my file. It played over my headphones just fine. I closed Audacity, then immediately opened it again to select a different file to edit. As Audacity opened I heard an audible ‘click’ over my headphones. I could no longer hear anything over my headphones whether in Audacity or via browser/youtube or other media player.
I discovered an AskUbuntu question with the same problem. An answer there said that we just needed to open Audacity and select Internal Mic:0. Tried that, and presto had audio over my headphones again.
Another answer on the same AU question recommended upgrading from 2.1.2 to the current (then) version of 2.2.0 to get around the bug in the future. So, I uninstalled 2.1.2, and installed 2.2.2 from the ubuntuhandbook repo.
Opened Audacity 2.2.2, only to discover that I now have no headphone volume again, and this time changing the output to Internal Mic:0 did not work. In fact, I cannot get headphone output on any of the 10 output options. Nothing plays over headphones now, not youtube/browser, not files in VLC.
All of this occurred in less than 5 minutes. Installing Audacity resulted in losing the ability to listen to anything on my laptop over headphones.
Please help. Like many of us, I have an extremely busy and demanding project/work schedule and did not anticipate losing a very basic and integral laptop function, or spending untold hours researching how to fix this inexplicable problem.