For a couple days now, Gmail unexpectedly gets its red "using microphone" circle on the tab even if I wasn't using hangouts or my microphone. Any idea why this is happening? This is on a laptop running on Windows 10 (From what I found on the meta, this was the best place to ask questions about Gmail, so sorry if I asked on the wrong SE.)
Have you considered seeing if an extension has access to your microphone on Google Apps? If it's not a clean install of chrome and you've previously installed chrome extensions the microphone may be in use by one of these extensions.
The only other thing I could think of is if you have a Google Voice or Hangouts conversation open that you are unaware of... but I highly doubt this would be the case with your issue.