The short story:

in the address bar in Chrome,  


chrome://settings/content/microphone


You can select the microphone that you use and deny access


The long story:

  1. Click the Chrome menu Chrome menu on the browser toolbar.
  2. Select Settings.
  3. Click Show advanced settings.
  4. In the "Privacy" section, click Content settings.
  5. In the "Media" section:
    • Ask when a site requires access to your camera and microphone: Select this option if you want Chrome to alert you whenever a site requests access to your camera and microphone.
    • Do not allow sites to access your camera and microphone: Select this option to automatically deny any site requests to access your camera and microphone.
  6. Click Manage exceptions to remove previously-granted permissions for specific sites.