Source: http://lifehacker.com/mute-mic-prevents-your-phones-microphone-from-recordin-1541038683
Android: Your phone is a hot bed of paranoia-inducing sensors. If you're worried about your microphone being used to record audio surreptitiously—or you'd like to do something simple like record a video without sound—Mute Mic can block other apps from using your mic.
The app is a one-button affair that mutes the microphone input volume system-wide. There are no settings or extra buttons to fiddle with. Just tap the button and you're done. This is particularly handy if you need to restrict the microphone permission on an app that you need, but that might be requesting too many permissions.
Mute Mic | Google Play Store via Ghacks
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