All the links I could find on how to manage this feature are out of date, even Google's support article.
Chrome actually doesn't work that way for me on Version 43.0.2357.130 m (64-bit).
The first time I clicked on the microphone on the Google search page I got this dialog:
I chose "No thanks."
Now when I click on the microphone on the Google search page I get this:
Notice the red dot on the tab. It's listening.
This post isn't about how to manage Google's voice search.
It's about how Google snuck the bits into the open source Chromium project.
Steve Gibson's Security Now is one of my regular podcasts. A recent episode covered the concern over Google inserting a binary "blob" into Chromium.
Audio Capture Allowed: Yes
9TO5Google had a good article on the concern.
The extension that powers Chrome’s voice search is not only downloaded automatically upon installing and launching the browser, but it’s also downloaded automatically in the Chromium open source version of the browser; the extension isn’t listed in the chrome://extensions UI...
...the open source version of the browser, which is not owned by Google, automatically installs proprietary Google technology for both managing whether the microphone is enabled and listening for hotwords. [emphasis original]What's happened to "Don't be evil?"